A101280 -id:A101280 - cp's OEIS frontend

A055151 Triangular array of Motzkin polynomial coefficients.

1, 1, 1, 1, 1, 3, 1, 6, 2, 1, 10, 10, 1, 15, 30, 5, 1, 21, 70, 35, 1, 28, 140, 140, 14, 1, 36, 252, 420, 126, 1, 45, 420, 1050, 630, 42, 1, 55, 660, 2310, 2310, 462, 1, 66, 990, 4620, 6930, 2772, 132, 1, 78, 1430, 8580, 18018, 12012, 1716, 1, 91, 2002, 15015, 42042

Offset: 0

Michael Somos, Jun 14 2000

T(n,k) = number of Motzkin paths of length n with k up steps. T(n,k)=number of 0-1-2 trees with n edges and k+1 leaves, n>0. (A 0-1-2 tree is an ordered tree in which every vertex has at most two children.) E.g., T(4,1)=6 because we have UDHH, UHDH, UHHD, HHUD, HUHD, HUDH, where U=(1,1), D(1,-1), H(1,0). - Emeric Deutsch, Nov 30 2003
Coefficients in series reversion of x/(1+H*x+U*D*x^2) corresponding to Motzkin paths with H colors for H(1,0), U colors for U(1,1) and D colors for D(1,-1). - Paul Barry, May 16 2005
Eigenvector equals A119020, so that A119020(n) = Sum_{k=0..[n/2]} T(n,k)*A119020(k). - Paul D. Hanna, May 09 2006
Row reverse of A107131. - Peter Bala, May 07 2012
Also equals the number of 231-avoiding permutations of n+1 for which descents(w) = peaks(w) = k, where descents(w) is the number of positions i such that w[i]>w[i+1], and peaks(w) is the number of positions i such that w[i-1]w[i+1]. For example, T(4,1) = 6 because 13245, 12435, 14235, 12354, 12534, 15234 are the only 231-avoiding permutations of 5 elements with descents(w) = peaks(w) = 1. - Kyle Petersen, Aug 02 2013
Apparently, a refined irregular triangle related to this triangle (and A097610) is given in the Alexeev et al. link on p. 12. This entry's triangle is also related through Barry's comment to A125181 and A134264. The diagonals of this entry are the rows of A088617. - Tom Copeland, Jun 17 2015
The row length sequence of this irregular triangle is A008619(n) = 1 + floor(n/2). - Wolfdieter Lang, Aug 24 2015

			The irregular triangle T(n,k) begins:
n\k 0  1   2    3   4  5 ...
0:  1
1:  1
2:  1  1
3:  1  3
4:  1  6   2
5:  1 10  10
6:  1 15  30    5
7:  1 21  70   35
8:  1 28 140  140  14
9:  1 36 252  420 126
10: 1 45 420 1050 630 42
... reformatted. - _Wolfdieter Lang_, Aug 24 2015

Miklos Bona, Handbook of Enumerative Combinatorics, CRC Press (2015), page 617, Corollary 10.8.2
T. K. Petersen, Eulerian Numbers, Birkhauser, 2015, Section 4.3.

Alois P. Heinz, Rows n = 0..200, flattened
N. Alexeev, J. Andersen, R. Penner, and P. Zograf, Enumeration of chord diagrams on many intervals and their non-orientable analogs, arXiv:1307.0967 [math.CO], 2013-2014.
Marcello Artioli, Giuseppe Dattoli, Silvia Licciardi, and Simonetta Pagnutti, Motzkin Numbers: an Operational Point of View, arXiv:1703.07262 [math.CO], 2017.
Paul Barry, The Gamma-Vectors of Pascal-like Triangles Defined by Riordan Arrays, arXiv:1804.05027 [math.CO], 2018.
Paul Barry, On the f-Matrices of Pascal-like Triangles Defined by Riordan Arrays, arXiv:1805.02274 [math.CO], 2018.
Colin Defant, Postorder Preimages, arXiv preprint arXiv:1604.01723 [math.CO], 2016.
Colin Defant, Troupes, Cumulants, and Stack-Sorting, arXiv:2004.11367 [math.CO], 2020.
Samuele Giraudo, Tree series and pattern avoidance in syntax trees, arXiv:1903.00677 [math.CO], 2019.
Thomas Grubb and Frederick Rajasekaran, Set Partition Patterns and the Dimension Index, arXiv:2009.00650 [math.CO], 2020. Mentions this sequence.
Paul W. Lapey and Aaron Williams, A Shift Gray Code for Fixed-Content Łukasiewicz Words, Williams College, 2022.
Shi-Mei Ma, On gamma-vectors and the derivatives of the tangent and secant functions, arXiv:1304.6654 [math.CO], 2013.
E. Marberg, Actions and identities on set partitions, arXiv preprint arXiv:1107.4173 [math.CO], 2011-2012.
MathOverflow, Motzkin polynomials and enumeration of chord diagrams.
Jean-Christophe Novelli and Jean-Yves Thibon, Noncommutative Symmetric Functions and Lagrange Inversion II: Noncrossing partitions and the Farahat-Higman algebra, arXiv:2106.08257 [math.CO], 2021-2022. See p. 32.
A. Postnikov, V. Reiner, and L. Williams, Faces of generalized permutohedra, arXiv:math/0609184 [math.CO], 2006-2007.
Tad White, Quota Trees, arXiv:2401.01462 [math.CO], 2024. See p. 20.
Claude Zeller and Robert Cordery, Light scattering as a Poisson process and first passage probability, arXiv:1906.11131 [cond-mat.stat-mech], 2019.

A107131 (row reversed), A080159 (with trailing zeros), A001006 = row sums, A000108(n) = T(2n, n), A001700(n) = T(2n+1, n), A119020 (eigenvector), A001263 (Narayana numbers), A089627 (gamma vectors of type B associahedra), A101280 (gamma vectors of type A permutohedra).
Cf. A125181, A134264, A088617, A161642, A258820, A003989, A008315, A091156, A011973, A097610, A126120.
Cf. A014531.

b:= proc(x, y) option remember;
      `if`(y>x or y<0, 0, `if`(x=0, 1, expand(
       b(x-1, y) +b(x-1, y+1) +b(x-1, y-1)*t)))
    end:
T:= n-> (p-> seq(coeff(p, t, i), i=0..degree(p)))(b(n, 0)):
seq(T(n), n=0..20);  # Alois P. Heinz, Feb 05 2014

m=(1-x-(1-2x+x^2-4x^2y)^(1/2))/(2x^2 y); Map[Select[#,#>0&]&, CoefficientList[ Series[m,{x,0,15}],{x,y}]]//Grid (* Geoffrey Critzer, Feb 05 2014 *)
p[n_] := Hypergeometric2F1[(1-n)/2, -n/2, 2, 4 x]; Table[CoefficientList[p[n], x], {n, 0, 13}] // Flatten (* Peter Luschny, Jan 23 2018 *)

{T(n, k) = if( k<0 || 2*k>n, 0, n! / ((n-2*k)! * k! * (k+1)!))}

{T(n, k) = if( k<0 || 2*k>n, 0, polcoeff( polcoeff( 2 / (1 - x + sqrt((1 - x)^2 - 4*y*x^2 + x * O(x^n))), n), k))} /* Michael Somos, Feb 14 2006 */

{T(n, k) = n++; if( k<0 || 2*k>n, 0, polcoeff( polcoeff( serreverse( x / (1 + x + y*x^2) + x * O(x^n)), n), k))} /* Michael Somos, Feb 14 2006 */

T(n,k) = n!/((n-2k)! k! (k+1)!) = A007318(n, 2k)*A000108(k). - Henry Bottomley, Jan 31 2003
E.g.f. row polynomials R(n,y): exp(x)*BesselI(1, 2*x*sqrt(y))/(x*sqrt(y)). - Vladeta Jovovic, Aug 20 2003
G.f. row polynomials R(n,y): 2 / (1 - x + sqrt((1 - x)^2 - 4 *y * x^2)).
From Peter Bala, Oct 28 2008: (Start)
The rows of this triangle are the gamma vectors of the n-dimensional (type A) associahedra (Postnikov et al., p. 38). Cf. A089627 and A101280.
The row polynomials R(n,x) = Sum_{k = 0..n} T(n,k)*x^k begin R(0,x) = 1, R(1,x) = 1, R(2,x) = 1 + x, R(3,x) = 1 + 3*x. They are related to the Narayana polynomials N(n,x) := Sum_{k = 1..n} (1/n)*C(n,k)*C(n,k-1)*x^k through x*(1 + x)^n*R(n, x/(1 + x)^2) = N(n+1,x). For example, for n = 3, x*(1 + x)^3*(1 + 3*x/(1 + x)^2) = x + 6*x^2 + 6*x^3 + x^4, the 4th Narayana polynomial.
Recursion relation: (n + 2)*R(n,x) = (2*n + 1)*R(n-1,x) - (n - 1)*(1 - 4*x)*R(n-2,x), R(0,x) = 1, R(1,x) = 1. (End)
G.f.: M(x,y) satisfies: M(x,y)= 1 + x M(x,y) + y*x^2*M(x,y)^2. - Geoffrey Critzer, Feb 05 2014
T(n,k) = A161642(n,k)*A258820(n,k) = (binomial(n,k)/A003989(n+1, k+1))* A258820(n,k). - Tom Copeland, Jun 18 2015
Let T(n,k;q) = n!*(1+k)/((n-2*k)!*(1+k)!^2)*hypergeom([k,2*k-n],[k+2],q) then T(n,k;0) = A055151(n,k), T(n,k;1) = A008315(n,k) and T(n,k;-1) = A091156(n,k). - Peter Luschny, Oct 16 2015
From Tom Copeland, Jan 21 2016: (Start)
Reversed rows of A107131 are rows of this entry, and the diagonals of A107131 are the columns of this entry. The diagonals of this entry are the rows of A088617. The antidiagonals (bottom to top) of A088617 are the rows of this entry.
O.g.f.: [1-x-sqrt[(1-x)^2-4tx^2]]/(2tx^2), from the relation to A107131.
Re-indexed and signed, this triangle gives the row polynomials of the compositional inverse of the shifted o.g.f. for the Fibonacci polynomials of A011973, x / [1-x-tx^2] = x + x^2 + (1+t) x^3 + (1+2t) x^4 + ... . (End)
Row polynomials are P(n,x) = (1 + b.y)^n = Sum{k=0 to n} binomial(n,k) b(k) y^k = y^n M(n,1/y), where b(k) = A126120(k), y = sqrt(x), and M(n,y) are the Motzkin polynomials of A097610. - Tom Copeland, Jan 29 2016
Coefficients of the polynomials p(n,x) = hypergeom([(1-n)/2, -n/2], [2], 4x). - Peter Luschny, Jan 23 2018
Sum_{k=1..floor(n/2)} k * T(n,k) = A014531(n-1) for n>1. - Alois P. Heinz, Mar 29 2020

A008303 Triangle read by rows: T(n,k) (n >= 1, 0 <= k <= ceiling(n/2)-1) = number of permutations of [n] with k peaks.

Original entry on oeis.org

1, 2, 4, 2, 8, 16, 16, 88, 16, 32, 416, 272, 64, 1824, 2880, 272, 128, 7680, 24576, 7936, 256, 31616, 185856, 137216, 7936, 512, 128512, 1304832, 1841152, 353792, 1024, 518656, 8728576, 21253376, 9061376, 353792, 2048, 2084864, 56520704, 222398464, 175627264, 22368256

Offset: 1

N. J. A. Sloane

From Petros Hadjicostas, Aug 06 2019: (Start)
André (1895) first defined these numbers. In his notation, T(n, k) = Q(n+1, 2*(k+1)) for n >= 1 and 0 <= k <= ceiling(n/2)-1.
His triangle is as follows (p. 148):
  Q_{2,2}
  Q_{3,2}
  Q_{4,2} Q_{4,4}
  Q_{5,2} Q_{5,4}
  Q_{6,2} Q_{6,4} Q_{6,6}
  Q_{7,2} Q_{7,4} Q_{7,6}
  ...
He has Q(n, s) = 0 when either s is odd, or n <= 1, or s > n. Also, Q_{n,2} = 2^(n-2) for n >= 2.
His recurrence is Q(n, s) = s * Q(n-1, s) + (n - s + 1) * Q(n-1, s-2) for n >= 3 and s >= 2. (Obviously, for s odd, we get Q(n, s) = 0 + 0 = 0.)
In terms of the current array, André's (1895) recurrence becomes T(n, k) = (2*k + 2) * T(n-1, k) + (n - 2*k) * T(n-1, k-1) for n >= 2 and 1 <= k <= n with T(n, 0) = 2^(n-1) for n >= 1. In this recurrence, we assume T(n, k) = 0 for k >= ceiling(n/2) or k < 0. (End)
From Petros Hadjicostas, Aug 07 2019: (Start)
We clarify further the quantity Q(n, s) defined by André (1895). In his paper, André considers circular permutations of [n] and deals with maxima, minima, and so-called "séquences" in a permutation.
The term "séquence" in a permutation, as used by André in several of his papers in the 19th century, means a list of consecutive numbers in the permutation that go from a maximum to a minimum, or vice versa, and do not contain any interior minima or maxima. This terminology is also repeated in Ex. 13 (pp. 260-261) by Comtet (even though he refers to the corresponding indices rather than the numbers in the permutation itself).
Some authors call these so-called "séquences" (defined by André and Comtet) "alternate runs" (or just "runs"). Here we are actually dealing with "circular runs" if we read these so-called "séquences" in ascending order in one of the two directions on a circle.
Q(n, s) is the number of circular permutations of [n] (out of the (n-1)! in total) that have exactly s of these so-called "séquences" ("alternate runs").
André (1895) proves that, in a circular permutation of [n], the number of maxima equals the number of minima and that the number of his so-called "séquences" ("alternate runs") is always even (i.e., Q(n, s) = 0 for s odd).
He also shows that, if v = floor(n/2), then the only possible values for the length of a so-called "séquence" ("alternate run") in a circular permutation of [n] are 2, 4, ..., 2*v. That is why Q(n, s) = 0 when either s is odd, or n <= 1, or s > n.
Note that Sum_{t = 1..floor(n/2)} Q_{n, 2*t} = Sum_{t = 1..floor(n/2)} T(n-1, t-1) = (n-1)! = total number of circular permutations of [n].
Since T(n, k) = Q(n+1, 2*(k+1)) for n >= 1 and 0 <= k <= ceiling(n/2)-1, we conclude that the number of (linear) permutations of [n] with k peaks equals the number of circular permutations of [n+1] with exactly 2*(k+1) of these so-called "séquences" ("alternate runs"). (End)
From Petros Hadjicostas, Aug 08 2019: (Start)
The author of this array indirectly assumes that a "peak" of a (linear) permutation of [n] is an interior maximum of the permutation; i.e., we ignore maxima at the endpoints of a permutation.
Similarly, a "valley" of a (linear) permutation of [n] is an interior minimum of the permutation; i.e., we ignore minima at the endpoints of the permutation.
Since the complement of a permutation a_1 a_2 ... a_n (using one-line notation, not cycle notation) is (n+1-a_1) (n+1-a_2) ... (n+1-a_n), it follows that, for n >= 2 and 0 <= k <= ceiling(n/2) - 1, T(n, k) is also the number of (linear) permutations of [n] with exactly k valleys. (End)

			Triangle T(n,k) (with rows n >= 1 and columns k >= 0) starts as follows:
  [ 1]    1;
  [ 2]    2;
  [ 3]    4,       2;
  [ 4]    8,      16;
  [ 5]   16,      88,      16;
  [ 6]   32,     416,     272;
  [ 7]   64,    1824,    2880,     272;
  [ 8]  128,    7680,   24576,    7936;
  [ 9]  256,   31616,  185856,  137216,    7936;
  [10]  512,  128512, 1304832, 1841152,  353792;
    A000079, A000431, A000487, A000517, A179708, ...
T(3,1) = 2 because we have 132 and 231.
From _Petros Hadjicostas_, Aug 07 2019: (Start)
In terms of André's (1895) notation (see the comments above), we have Q(4, 2) = T(3, 0) = 4 and Q(4, 4) = T(3, 1) = 2.
Out of the (4-1)! = 6 circular permutations of [4], each of the permutations 1324 and 1423 has exactly 4 so-called "séquences" ("alternate runs"), while each of the rest (1234, 1243, 1342, and 1432) has exactly 2 so-called "séquences" ("alternate runs").
In detail, we list the so-called "séquences" ("alternate runs") of the above circular permutations:
  1234 --> 1234 and 41 (maximum 4 and minimum 1).
  1243 --> 124 and 431 (maximum 4 and minimum 1).
  1324 --> 13, 32, 24, and 41 (maxima 3, 4, and minima 1, 2).
  1342 --> 134 and 421 (maximum 4 and minimum 1).
  1423 --> 14, 42, 23, and 31 (maxima 3, 4 and minima 1, 2),
  1432 --> 14 and 4321 (maximum 4 and minimum 1).
(End)

Florence Nightingale David and D. E. Barton, Combinatorial Chance, Charles Griffin, 1962; see Table 10.6, p. 163. [They use the notation T_{N,t^*}^{**}, where N is the length of the permutation and t^* is the number of peaks in the permutation. They also give André's recurrence. So, here n = N and k = t^*. - Petros Hadjicostas, Aug 09 2019]
Florence Nightingale David, Maurice George Kendall, and D. E. Barton, Symmetric Functions and Allied Tables, Cambridge, 1966, p. 261, Table 7.3.
I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983, Ex. 3.3.46. - Emeric Deutsch, Jul 26 2009
T. K. Petersen, Eulerian Numbers, Birkhäuser, 2015, Chapter 4.

Alois P. Heinz, Rows n = 1..200, flattened (first 30 rows from Vincenzo Librandi)
Max A. Alekseyev, On the number of permutations with bounded run lengths, arXiv preprint arXiv:1205.4581 [math.CO], 2012-2013. - From _N. J. A. Sloane_, Oct 23 2012
Désiré André, Mémoire sur les séquences des permutations circulaires, Bulletin de la S. M. F., tome 23 (1895), pp. 122-184.
T. Austin, R. Fagen, T. Lehrer, and W. Penney, The distribution of the number of locally maximal elements in a random sample, Ann. Math. Statist. 28 (1957), 786-790. - _Ira M. Gessel_, Aug 06 2014
Jean-Luc Baril and José L. Ramírez, Some distributions in increasing and flattened permutations, arXiv:2410.15434 [math.CO], 2024. See p. 3.
S. Billey, K. Burdzy, and B. E. Sagan, Permutations with given peak set, arXiv: 1209.0693 [math.CO], 2012.
S. Billey, K. Burdzy, and B. E. Sagan, Permutations with given peak set, J. Int. Seq. 16 (2013), #13.6.1.
C.-O. Chow and S.-M. Ma, Counting signed permutations by their alternating runs, Discrete Mathematics, 323 (2014), 49-57.
C.-O. Chow, S.-M. Ma, T. Mansour, and M. Shattuck, Counting permutations by cyclic peaks and valleys, Annales Mathematicae et Informaticae 43 (2014), 43-54.
Kieran Clenaghan, In Praise of Sequence (Co-)Algebra and its implementation in Haskell, arXiv:1812.05878 [math.CO], 2019. See page 36.
Colin Defant, Troupes, Cumulants, and Stack-Sorting, arXiv:2004.11367 [math.CO], 2020.
Ming-Jian Ding and Bao-Xuan Zhu, Some results related to Hurwitz stability of combinatorial polynomials, Advances in Applied Mathematics, Volume 152, (2024), 102591. See p. 13.
S. Elizalde and M. Noy, Consecutive patterns in permutations, Adv. Appl. Math. 30 (2003), 110-125; see Section 5.
R. C. Entringer, Enumeration of permutations of (1,...,n) by number of maxima, Duke Math. J. 36 (1969), 575-579. - _Ira M. Gessel_, Oct 23 2013
C. J. Fewster and D. Siemssen, Enumerating Permutations by their Run Structure, arXiv preprint arXiv:1403.1723 [math.CO], 2014.
FindStat - Combinatorial Statistic Finder, The number of inner peaks of a permutation, The number of peaks of a permutation, The number of valleys of a permutation.
W. O. Kermack and A. G. McKendrick, Some distributions associated with a randomly arranged set of numbers, Proc. Royal Soc. of Edinburgh 67 (1937), 332-376.
W. O. Kermack and A. G. McKendrick, Some properties of points arranged on a Möbius surface, Mathematical Gazette 22 (1938), 66-72.
Shi-Mei Ma, Derivative polynomials and permutations by numbers of interior peaks and left peaks, arXiv preprint arXiv:1106.5781 [math.CO], 2011.
Shi-Mei Ma, Enumeration of permutations by number of alternating runs, Discrete Math., 313 (2013), 1816-1822.
S.-M. Ma, T. Mansour, and D. G. L. Wang, Combinatorics of Dumont differential system on the Jacobi elliptic functions, arXiv preprint arXiv:1403.0233 [math.CO], 2014.
Shi-Mei Ma, Toufik Mansour, David G.L. Wang, and Yeong-Nan Yeh, Several variants of the Dumont differential system and permutation statistics, Science China Mathematics 60 (2018).
Shi-Mei Ma, Jun Ma, Jean Yeh, and Yeong-Nan Yeh, The 1/k-Eulerian polynomials of type B, arXiv:2001.07833 [math.CO], 2020.
A. Mendes and J. B. Remmel, Permutations and words counted by consecutive patterns, Adv. Appl. Math. 37(4) (2006), 443-480.
Tom Roberts and Thomas Prellberg, Improving Convergence of Generalised Rosenbluth Sampling for Branched Polymer Models by Uniform Sampling, arXiv:2401.12201 [cond-mat.stat-mech], 2024. See p. 14.
Louis W. Shapiro, Wen-Jin Woan, and Seyoum Getu, Runs, slides and moments, SIAM J. Algebraic and Discrete Methods 4 (1983), 459-466; see p. 461.
Bao-Xuan Zhu, Stieltjes moment properties and continued fractions from combinatorial triangles, arXiv:2007.14924 [math.CO], 2020, see p. 27.
Yan Zhuang, Monoid networks and counting permutations by runs, arXiv preprint arXiv:1505.02308 [math.CO], 2015.
Yan Zhuang, Counting permutations by runs, J. Comb. Theory Ser. A 142 (2016), pp. 147-176.

From Emeric Deutsch, Jul 26 2009: (Start)
Sum of entries in row n is n! = A000142(n).
T(n,0) = 2^(n-1) = A000079(n-1).
T(n,1) = A000431(n).
T(n,2) = A000487(n).
T(n,3) = A000517(n).
T(2n, n-1) = T(2n+1, n) = A000182(n+1) (the tangent numbers). (End)
Columns k = 0-6 give: A011782, A000431, A000487, A000517, A179708, A179709, A179710.
Cf. A000111, A000182, A090672, A101280, A185896, A242783, A242784.

# The Maple program yields (by straightforward counting) the generating polynomial of the row n specified in the program.
n := 8: with(combinat): P := permute(n): st := proc (p) local ct, j: ct := 0: for j from 2 to nops(p)-1 do if p[j-1] < p[j] and p[j+1] < p[j] then ct := ct+1 else end if end do: ct end proc: sort(add(t^st(P[j]), j = 1 .. factorial(n))); # Emeric Deutsch, Jul 26 2009
# Second Maple program:
a := 1+sqrt(1-t): b := 1-sqrt(1-t): G := (exp(b*z)-exp(a*z))/(b*exp(a*z)-a*exp(b*z)): Gser := simplify(series(G, z = 0, 15)): for n to 12 do P[n] := sort(expand(factorial(n)*coeff(Gser, z, n))) end do: for n to 12 do seq(coeff(P[n], t, j), j = 0 .. ceil((1/2)*n)-1) end do; # yields sequence in triangular form - Emeric Deutsch, Jul 26 2009
# Third Maple program:
b:= proc(u, o, t) option remember; expand(`if`(u+o=0, 1,
      add(b(u-j, o+j-1, 0)*x^t, j=1..u)+
      add(b(u+j-1, o-j, 1), j=1..o)))
    end:
T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n, 0$2)):
seq(T(n), n=1..15);  # Alois P. Heinz, May 22 2014
# Recurrence of D. André (1895).
T := proc(n, k) option remember;
if n < 1 or 2*k > (n-1) then return 0 fi;
if k = 0 then return 2^(n-1) fi;
(2*k + 2)*T(n-1, k) + (n - 2*k)*T(n-1, k-1) end:
seq(seq(T(n, k), k=0..(n-1)/2), n=1..12); # Peter Luschny, Aug 06 2019

From Luc Roy, Jul 08 2010: (Start)
It appears that one-half of the sequence A008303 can be obtained with this Mathematica program:
Expand[CoefficientList[Simplify[InverseSeries[Integrate[
Series[(1 + m Sinh[x]^2)^(-1), {x, 0, 15}, {m, 0, 15}], x]]], x]
Denominator[CoefficientList[Series[Exp[x], {x, 0, 15}], x]]]
(* Mathematica Output of Luc Roy's program *)
{0, 1, 0, 2 m, 0, 8 m + 16 m^2, 0, 32 m + 416 m^2 + 272 m^3, 0, 128 m + 7680 m^2 + 24576 m^3 + 7936 m^4, 0, 512 m + 128512 m^2 + 1304832 m^3 + 1841152 m^4 + 353792 m^5, 0, 2048 m + 2084864 m^2 + 56520704 m^3 + 222398464 m^4 + 175627264 m^5 + 22368256 m^6, 0, 8192 m + 33497088 m^2 + 2230947840 m^3 + 20261765120 m^4 + 41731645440 m^5 + 21016670208 m^6 + 1903757312 m^7}
(End)
(* Another Mathematica program *)
m = 14; a = 1 + Sqrt[1 - t]; b = 1 - Sqrt[1 - t];
g[z_] = (E^(b*z) - E^(a*z))/(b*E^(a*z) - a*E^(b*z));
gser = Series[g[z], {z, 0, m}];
Do[p[n]=n!*Coefficient[gser, z, n]//Simplify, {n, 0, m}];
Flatten[ Table[ Coefficient[p[n], t, j], {n, 0, m}, {j, 0, Ceiling[n/2] - 1}]]
(* Jean-François Alcover, May 27 2011, after Emeric Deutsch *)
(* To get the triangle from Jean-François Alcover's Mathematica program *)
FormTable[Table[Coefficient[p[n], t, j], {n, 0, m}, {j, 0, Ceiling[n/2] - 1}]]
(* Petros Hadjicostas, Aug 06 2019 *)
gf := Sqrt[x - 1] Cot[y Sqrt[x - 1]] - 1; ser := Series[1/gf, {y, 0, 16}];
cy[n_] := n! Coefficient[ser, y, n]; row[n_] := CoefficientList[cy[n], x];
Table[row[n], {n, 1, 12}] // Flatten (* Peter Luschny, Aug 06 2019 *)

{T(n, k) = if(n<1, 0, my(z = sqrt(1 - y + y*O(y^(n\2)))); n!*polcoef(polcoef(z/(z - tanh(x*z)), n, x), k))}; /* Michael Somos, May 24 2023 */

From Emeric Deutsch, Jul 26 2009: (Start)
E.g.f.: G(t,z)=[exp(bz)-exp(az)]/[b*exp(az)-a*exp(bz)], where a+b=2 and ab=t, i.e., a=1+sqrt(1-t), b=1-sqrt(1-t) (see the Goulden-Jackson reference). -
Sum_{k>=0} k*T(n,k) = n!*(n-2)/3 = A090672(n-1).
Row n has ceiling(n/2) terms. (End)
E.g.f.: tan(t*sqrt(x-1))/(sqrt(x-1)-tan(t*sqrt(x-1))) = Sum_{n>=0} P(n,x)*t^n/n! = t + 2*t^2/2! + (4+2*x)*t^3/3! + (8+16*x)*t^4/4! + .... The row generating polynomials P(n,x) satisfy x^(n-1)*P(n,1+1/x^2) = R(n-1,x), where R(n,x) are the row polynomials of A185896. A000670(n) = (3/2)^(n-1)*P(n,8/9). - Peter Bala, Oct 14 2011
From Jinyuan Wang, Dec 28 2020: (Start)
T(n, k) = (n - 2*k + 2)*T(n-1, k-1) + 2*k*T(n-1, k) for n > 1 and k > 1; T(n, 1) = 2^(n - 1); T(1, k) = 0 for k > 1.
T(2*k-1, k) = A000182(k). (End)
From Ammar Khatab, Aug 17 2024: (Start)
T(2*n,k) = 4^(n-k+1)* Sum_{p=0..k} (-1)^p * (2*p+2*n-2*k-1)/(p+2*n-2*k-1) binomial(p+2*n-2*k-1,p) (A008292(2*n,k-p+1)+A008292(2*n,2*n+p-k) ) for n>0.
T(2*n+1,k) = 4^(n-k)* Sum_{p=0..k} (-1)^p * (p+n-k)/(p+2*n-2*k) binomial(p+2*n-2*k,p) (A008292(2*n+1,k-p+1)+A008292(2*n,2*n+p-k+1) ) for k<>n. (End)

Additional comments from Emeric Deutsch, May 08 2004
More terms from R. J. Mathar and Vladeta Jovovic, Jun 26 2007
Corrected by Emeric Deutsch, Jul 26 2009
Edited definition - N. J. A. Sloane, May 25 2023

A089627 T(n,k) = binomial(n,2k)binomial(2*k,k) for 0 <= k <= n, triangle read by rows.

Original entry on oeis.org

1, 1, 0, 1, 2, 0, 1, 6, 0, 0, 1, 12, 6, 0, 0, 1, 20, 30, 0, 0, 0, 1, 30, 90, 20, 0, 0, 0, 1, 42, 210, 140, 0, 0, 0, 0, 1, 56, 420, 560, 70, 0, 0, 0, 0, 1, 72, 756, 1680, 630, 0, 0, 0, 0, 0, 1, 90, 1260, 4200, 3150, 252, 0, 0, 0, 0, 0, 1, 110, 1980, 9240, 11550, 2772, 0, 0, 0, 0, 0, 0, 1, 132, 2970, 18480, 34650, 16632, 924, 0, 0, 0, 0, 0, 0, 1, 156, 4290, 34320, 90090, 72072, 12012, 0, 0, 0, 0, 0, 0, 0, 1, 182, 6006, 60060, 210210, 252252, 84084, 3432, 0, 0, 0, 0, 0, 0, 0

Offset: 0

Philippe Deléham, Dec 31 2003

The rows of this triangle are the gamma vectors of the n-dimensional type B associahedra (Postnikov et al., p.38 ). Cf. A055151 and A101280. - Peter Bala, Oct 28 2008
T(n,k) is the number of Grand Motzkin paths of length n having exactly k upsteps (1,1). Cf. A109189, A055151. - Geoffrey Critzer, Feb 05 2014
The result Sum_{k = 0..floor(n/2)} C(n,2*k)*C(2*k,k)*x^k = (sqrt(1 - 4*x))^n* P(n,1/sqrt(1 - 4*x)) expressing the row polynomials of this triangle in terms of the Legendre polynomials P(n,x) is due to Catalan. See Laden, equation 7.10, p. 56. - Peter Bala, Mar 18 2018

			Triangle begins:
  1
  1,   0
  1,   2,    0
  1,   6,    0,     0
  1,  12,    6,     0,     0
  1,  20,   30,     0,     0,     0
  1,  30,   90,    20,     0,     0,   0
  1,  42,  210,   140,     0,     0,   0, 0
  1,  56,  420,   560,    70,     0,   0, 0, 0
  1,  72,  756,  1680,   630,     0,   0, 0, 0, 0
  1,  90, 1260,  4200,  3150,   252,   0, 0, 0, 0, 0
  1, 110, 1980,  9240, 11550,  2772,   0, 0, 0, 0, 0, 0
  1, 132, 2970, 18480, 34650, 16632, 924, 0, 0, 0, 0, 0, 0
Relocating the zeros to be evenly distributed and interpreting the triangle as the coefficients of polynomials
                     1
                     1
                 1 + 2 q^2
                 1 + 6 q^2
            1 + 12 q^2 +  6 q^4
            1 + 20 q^2 + 30 q^4
       1 + 30 q^2 +  90 q^4 +  20 q^6
       1 + 42 q^2 + 210 q^4 + 140 q^6
  1 + 56 q^2 + 420 q^4 + 560 q^6 + 70 q^8
then the substitution q^k -> 1/(floor(k/2)+1) gives the Motzkin numbers A001006.
- _Peter Luschny_, Aug 29 2011

Alois P. Heinz, Rows n = 0..140, flattened
Rui Duarte and António Guedes de Oliveira, A Famous Identity of Hajós in Terms of Sets, Journal of Integer Sequences, Vol. 17 (2014), #14.9.1.
Hyman N. Laden, An historical, and critical development of the theory of Legendre polynomials before 1900, Master of Arts Thesis, University of Maryland 1938.
Shi-Mei Ma, On gamma-vectors and the derivatives of the tangent and secant functions, arXiv:1304.6654 [math.CO], 2013.
A. Postnikov, V. Reiner, and L. Williams, Faces of generalized permutohedra, arXiv:math/0609184 [math.CO], 2006-2007.

Row sums A002426. Antidiagonal sums A098479.

Cf. A055151, A063007, A109187, A101280.

for i from 0 to 12 do seq(binomial(i, j)*binomial(i-j, j), j=0..i) od; # Zerinvary Lajos, Jun 07 2006
# Alternatively:
R := (n, x) -> simplify(hypergeom([1/2 - n/2, -n/2], [1], 4*x)):
Trow := n -> seq(coeff(R(n,x), x, j), j=0..n):
seq(print(Trow(n)), n=0..9); # Peter Luschny, Mar 18 2018

nn=15;mxy=(1-x-(1-2x+x^2-4x^2y)^(1/2))/(2x^2 y);Map[Select[#,#>0&]&, CoefficientList[Series[1/(1-x-2y x^2mxy),{x,0,nn}],{x,y}]]//Grid (* Geoffrey Critzer, Feb 05 2014 *)

T(n,k) = binomial(n,2*k)*binomial(2*k,k);
concat(vector(15, n, vector(n, k, T(n-1, k-1)))) \\ Gheorghe Coserea, Sep 01 2018

T(n,k) = n!/((n-2*k)!*k!*k!).
E.g.f.: exp(x)*BesselI(0, 2*x*sqrt(y)). - Vladeta Jovovic, Apr 07 2005
O.g.f.: ( 1 - x - sqrt(1 - 2*x + x^2 - 4*x^2*y))/(2*x^2*y). - Geoffrey Critzer, Feb 05 2014
R(n, x) = hypergeom([1/2 - n/2, -n/2], [1], 4*x) are the row polynomials. - Peter Luschny, Mar 18 2018
From Peter Bala, Jun 23 2023: (Start)
T(n,k) = Sum_{i = 0..k} (-1)^i*binomial(n, i)*binomial(n-i, k-i)^2. Cf. A063007(n,k) = Sum_{i = 0..k} binomial(n, i)^2*binomial(n-i, k-i).
T(n,k) = A063007(n-k,k); that is, the diagonals of this table are the rows of A063007. (End)

A094503 Triangle read by rows: coefficients d(n,k) of Andre polynomials D(x,n) = Sum_{k>0} d(n,k)*x^k.

Original entry on oeis.org

1, 1, 1, 1, 1, 4, 1, 11, 4, 1, 26, 34, 1, 57, 180, 34, 1, 120, 768, 496, 1, 247, 2904, 4288, 496, 1, 502, 10194, 28768, 11056, 1, 1013, 34096, 166042, 141584, 11056, 1, 2036, 110392, 868744, 1372088, 349504, 1, 4083, 349500, 4247720, 11204160, 6213288

Offset: 1

Philippe Deléham, Jun 09 2004

a(n,k) is the number of increasing 0-1-2 trees on [n] with k leaves. An increasing 0-1-2 tree on [n] is an unordered tree on [n], rooted at 1, in which each vertex has <= 2 children and the labels increase along each path from the root. Example: a(4,2)=4 counts the trees with edges as follows, {1->2->3,1->4}, {1->2->4,1->3}, {1->2->4,2->3}, {1->3->4,1->2}. - David Callan, Oct 24 2004

			Triangle begins:
  1
  1
  1  1
  1  4
  1 11   4
  1 26  34
  1 57 180 34
  ...
From _Peter Bala_, Jun 26 2012: (Start)
Recurrence equation: T(6,3) = 3*T(5,3) + 2*T(5,2) = 3*4 + 2*11 = 34.
n = 4: the 5 weighted non-plane increasing 0-1-2 trees on 4 vertices are
.........................................................
..4......................................................
..|......................................................
..3............4............4.............3.......3...4..
..|.........../............/............./.........\./...
..2......2...3........3...2.........4...2........(t)2....
..|.......\./..........\./...........\./............|....
..1.....(t)1.........(t)1..........(t)1.............1....
.........................................................
Hence row polynomial R(4,t) = (1 + 4*t)*t.
(End)

Alois P. Heinz, Rows n = 1..200, flattened
Paul Barry, Three Études on a sequence transformation pipeline, arXiv:1803.06408 [math.CO], 2018.
F. Bergeron, Ph. Flajolet, and B. Salvy, Varieties of Increasing Trees, Lecture Notes in Computer Science vol. 581, ed. J.-C. Raoult, Springer 1992, pp. 24-48.
David Callan, A note on downup permutations and increasing 0-1-2 trees
Chak-On Chow and Wai Chee Shiu, Counting Simsun Permutations by Descents, Ann. Comb. 15, 625-635 (2011). See p. 627 and comments section in A113897.
Ming-Jian Ding and Bao-Xuan Zhu, Some results related to Hurwitz stability of combinatorial polynomials, Advances in Applied Mathematics, Volume 152, (2024), 102591. See p. 35.
Filippo Disanto and Thomas Wiehe, Exact enumeration of cherries and pitchforks in ranked trees under the coalescent model, arXiv preprint arXiv:1112.1295 [math.CO], 2011-2012, see Y(x,z).
Filippo Disanto and Thomas Wiehe, Exact enumeration of cherries and pitchforks in ranked trees under the coalescent model, Math. Biosci. 242 (2013), no. 2, 195-200.
D. Dominici, Nested derivatives: A simple method for computing series expansions of inverse functions. arXiv:math/0501052v2 [math.CA], 2005.
Dominique Foata and Guoniu Han, Arbres minimax et polynomes d'André .
D. Foata and Guo-Niu Han, Arbres minimax et polynomes d'André, Adv. in Appl. Math., 27 (2001), no.2-3, 367-389.
Guo-Niu Han and Shi-Mei Ma, Derivatives, Eulerian polynomials and the g-indexes of Young tableaux, arXiv:2006.14064 [math.CO], 2020.
Shi-Mei Ma, Enumeration of permutations by number of alternating runs, Discrete Math., 313 (2013), 1816-1822.
Shi-Mei Ma, Qi Fang, Toufik Mansour, and Yeong-Nan Yeh, Alternating Eulerian polynomials and left peak polynomials, arXiv:2104.09374, 2021
Shi-Mei Ma and Yeong-Nan Yeh, The Peak Statistics on Simsun Permutations, Elect. J. Combin., 23 (2016), P2.14; arXiv preprint, arXiv:1601.06505 [math.CO], 2016.
E. Norton, Symplectic Reflection Algebras in Positive Characteristic as Ore Extensions, arXiv preprint arXiv:1302.5411 [math.RA], 2013.

Cf. A000012, A000295, A008292, A101280, A113897.

A094503:=proc(n,k) options remember: if(n=1 and k=1) then RETURN(1) elif(1<=k and k<=floor((n+1)/2) and n>=1) then RETURN(k*A094503(n-1,k)+(n+2-2*k)*A094503(n-1,k-1)) else RETURN(0) fi: end; seq(seq(A094503(n,k),k=1..floor((n+1)/2)),n=1..14);

t[1, 1] = 1; t[n_, k_] /; Not[1 <= k <= (n+1)/2] = 0; t[n_, k_] := t[n, k] = k*t[n-1, k] + (n+2-2*k)*t[n-1, k-1]; Table[t[n, k], {n, 0, 13}, {k, 1, (n + 1)/2}] // Flatten (* Jean-François Alcover, Nov 22 2012, after Maple *)

def p(n) :
    s = var('s'); u = sqrt(s^2-2)
    egf = u*x-2*ln((exp(u*x)*(1-s/u)+s/u+1)/2)
    return factorial(n+2)*egf.series(x,n+4).coefficient(x,n+2)
def A094503_row(n) : return [p(n).coefficient(s,n-2*i) for i in (0..n//2)]
for n in (0..6): print(A094503_row(n)) # Peter Luschny, Jul 01 2012

D(1, n) = A000111(n), Euler or up/down numbers. D(1/2, n) = A000142(n)*(1/2)^n. D(1/4, n) = A080795(n)*(1/4)^n.
From Peter Bala, Jun 26 2012: (Start):
Recurrence equation: T(n,k) = k*T(n-1,k) + (n+2-2*k)*T(n-1,k-1) for n >= 1 and 1 <= k <= floor((n+1)/2).
Let r(t) = sqrt(1-2*t) and w(t) = (1-r(t))/(1+r(t)). The e.g.f. is F(t,z) = r(t)*(1 + w(t)*exp(r(t)*z))/(1 - w(t)*exp(r(t)*z)) = 1 + t*z + t*z^2/2! + (t+t^2)*z^3/3! + (t+4*t^2)*z^4/4! + ... (Foata and Han, 2001, section 7).
Note that (F(2*t,z) - 1)/(2*t) is the e.g.f. for A101280.
The modified e.g.f. A(t,z) := (F(t,z) - 1)/t = z + z^2/2! + (1+t)*z^3/3! + (1+4*t)*z^4/4! + ... satisfies the autonomous partial differential equation dA/dz = 1 + A + 1/2*t*A^2 with A(t,0) = 1. It follows that the inverse function A(t,z)^(-1) may be expressed as an integral: A(t,z)^(-1) = Integral_{x = 0..z} 1/(1+x+1/2*t*x^2) dx.
Applying [Dominici, Theorem 4.1] to invert the integral gives the following method for calculating the row polynomials R(n,t) of the table: let f(t,x) = 1+x+1/2*t*x^2 and let D be the operator f(t,x)*d/dx. Then R(n+1,t) = t*D^n(f(t,x)) evaluated at x = 0.
By Bergeron et al., Theorem 1, the shifted row polynomial 1/t*R(n,t) is the generating function for rooted non-plane increasing 0-1-2 trees on n vertices, where the vertices of outdegree 2 have weight t and all other vertices have weight 1. An example is given below.
1/(2*t)*(1+t)^(n+1)*R(n,2*t/(1+t)^2) = the n-th Eulerian polynomial of A008292. For example, n = 5 gives 1/(2*t)*(1+t)^6*R(5,2*t/(1+t)^2) = 1 + 26*t + 66*t^2 + 26*t^3 + t^4.
A000142(n) = 2^n*R(n,1/2); A080795(n) = 4^n*R(n,1/4);
A000670(n) = 3/4*3^n*R(n,4/9); A004123(n+1) = 5/6*5^n*R(n,12/25).
(End)
There is a second family of polynomials which also matches the data and is different from the André polynomials as defined by Foata and Han (2001), formula 3.5. Let u = sqrt(s^2-2) and F(s,x) = u*x-2*log((exp(u*x)*(1-s/u)+s/u+1)/2), then for n>=0 the sequence of polynomials p_{n}(s) = (n+2)!*[x^(n+2)]F(s,x) starts 1, s, s^2+1, s^3+4*s, s^4+11*s^2+4, s^5+26*s^3+34*s, s^6+57*s^4+180*s^2+34, ... and the nonzero coefficients of these polynomials in descending order coincide with the sequence a(n). p_{n}(0) is an aerated version of the reduced tangent numbers, p_{2*n}(0) = A002105(n+1) for n>=0. In contrast, the André polynomials vanish at t=0 except for n=0. - Peter Luschny, Jul 01 2012
T(n,k) = A008303(n,k)/2^(n-k). - Ammar Khatab, Aug 17 2024

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A055151 Triangular array of Motzkin polynomial coefficients.

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A008303 Triangle read by rows: T(n,k) (n >= 1, 0 <= k <= ceiling(n/2)-1) = number of permutations of [n] with k peaks.

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A089627 T(n,k) = binomial(n,2*k)*binomial(2*k,k) for 0 <= k <= n, triangle read by rows.

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A094503 Triangle read by rows: coefficients d(n,k) of Andre polynomials D(x,n) = Sum_{k>0} d(n,k)*x^k.

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A333273 Irregular triangle read by rows: coefficients of q-Eulerian polynomials of Type B.

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A089627 T(n,k) = binomial(n,2k)binomial(2*k,k) for 0 <= k <= n, triangle read by rows.