A005572 -id:A005572 - cp's OEIS frontend

A118346 Central terms of pendular triangle A118345.

1, 1, 5, 30, 201, 1445, 10900, 85128, 682505, 5585115, 46461437, 391743850, 3340361700, 28755475180, 249572076200, 2181469638880, 19186562661273, 169677521094215, 1507881643936015, 13458730170115778, 120599648894147185

Offset: 0

Paul D. Hanna, Apr 26 2006

nonn

Also, g.f. A(x) = (1/x)*series_reversion of x/(1 + x*GF(A005572)), where GF(A005572) is the g.f. of A005572, which is the number of walks on cubic lattice starting and finishing on the xy plane and never going below it.

Seiichi Manyama, Table of n, a(n) for n = 0..1000

Cf. A118345, A118347, A118348, A118349.

R:=PowerSeriesRing(Rationals(), 30);
[1] cat Coefficients(R!( Reversion( x/((1+x)*(1+4*x+x^2)) ) )); // G. C. Greubel, Mar 17 2021

CoefficientList[1 +InverseSeries[Series[x/((1+x)*(1+4*x+x^2)), {x,0,30}]], x] (* G. C. Greubel, Mar 17 2021 *)

{a(n) = polcoeff(serreverse( x*(1-2*x+sqrt((1-2*x)*(1-6*x)+x*O(x^n)))/(2*(1-2*x)))/x, n)}

def A118346_list(prec):
    P. = PowerSeriesRing(ZZ, prec)
    return P( ( x/((1+x)*(1+4*x+x^2)) ).reverse() ).list()
a=A118346_list(31); [1]+a[1:] # G. C. Greubel, Mar 17 2021

G.f.: A=A(x) satisfies A = 1 - 2*x*A + 2*x*A^2 + x*A^3.
G.f.: A(x) = 1 + series_reversion( x/((1+x)*(1+4*x+x^2)) ).
G.f.: A(x) = (1/x)*series_reversion( x*(1-2*x + sqrt((1-2*x)*(1-6*x)))/(2*(1-2*x)) ).
For n>0: a(n) = (1/n)*Sum_{j=0..n} Sum_{i=0..n-1} ( binomial(n,j) * binomial(j,i) * binomial(n-j,2*j-n-i-1) * 5^(2*n-3*j+2*i+1) ). -Vladimir Kruchinin, Dec 26 2010

A247495 Generalized Motzkin numbers: Square array read by descending antidiagonals, T(n, k) = k![x^k](exp(nx)* BesselI_{1}(2*x)/x), n>=0, k>=0.

Original entry on oeis.org

1, 0, 1, 1, 1, 1, 0, 2, 2, 1, 2, 4, 5, 3, 1, 0, 9, 14, 10, 4, 1, 5, 21, 42, 36, 17, 5, 1, 0, 51, 132, 137, 76, 26, 6, 1, 14, 127, 429, 543, 354, 140, 37, 7, 1, 0, 323, 1430, 2219, 1704, 777, 234, 50, 8, 1, 42, 835, 4862, 9285, 8421, 4425, 1514, 364, 65, 9, 1

Offset: 0

Peter Luschny, Dec 11 2014

This two-dimensional array of numbers can be seen as a generalization of the Motzkin numbers A001006 for two reasons: The case n=1 reduces to the Motzkin numbers and the columns are the values of the Motzkin polynomials M_{k}(x) = sum_{j=0..k} A097610(k,j)*x^j evaluated at the nonnegative integers.

			Square array starts:
[n\k][0][1] [2]  [3]   [4]   [5]    [6]     [7]      [8]
[0]   1, 0,  1,   0,    2,    0,     5,      0,      14, ...  A126120
[1]   1, 1,  2,   4,    9,   21,    51,    127,     323, ...  A001006
[2]   1, 2,  5,  14,   42,  132,   429,   1430,    4862, ...  A000108
[3]   1, 3, 10,  36,  137,  543,  2219,   9285,   39587, ...  A002212
[4]   1, 4, 17,  76,  354, 1704,  8421,  42508,  218318, ...  A005572
[5]   1, 5, 26, 140,  777, 4425, 25755, 152675,  919139, ...  A182401
[6]   1, 6, 37, 234, 1514, 9996, 67181, 458562, 3172478, ...  A025230
A000012,A001477,A002522,A079908, ...
.
Triangular array starts:
              1,
             0, 1,
           1, 1, 1,
          0, 2, 2, 1,
        2, 4, 5, 3, 1,
      0, 9, 14, 10, 4, 1,
   5, 21, 42, 36, 17, 5, 1,
0, 51, 132, 137, 76, 26, 6, 1.

Seiichi Manyama, Antidiagonals n = 0..139, flattened

Main diagonal gives A247496.

Cf. A126120, A001006, A000108, A002212, A005572, A182401, A025230, A002522, A079908, A055151, A097610, A247497, A306684.

# RECURRENCE
T := proc(n,k) option remember; if k=0 then 1 elif k=1 then n else
(n*(2*k+1)*T(n,k-1)-(n-2)*(n+2)*(k-1)*T(n,k-2))/(k+2) fi end:
seq(print(seq(T(n,k),k=0..9)),n=0..6);
# OGF (row)
ogf := n -> (1-n*x-sqrt(((n-2)*x-1)*((n+2)*x-1)))/(2*x^2):
seq(print(seq(coeff(series(ogf(n),x,12),x,k),k=0..9)),n=0..6);
# EGF (row)
egf := n -> exp(n*x)*hypergeom([],[2],x^2):
seq(print(seq(k!*coeff(series(egf(n),x,k+2),x,k),k=0..9)),n=0..6);
# MOTZKIN polynomial (column)
A097610 := proc(n,k) if type(n-k,odd) then 0 else n!/(k!*((n-k)/2)!^2* ((n-k)/2+1)) fi end: M := (k,x) -> add(A097610(k,j)*x^j,j=0..k):
seq(print(seq(M(k,n),n=0..9)),k=0..6);
# OGF (column)
col := proc(n, len) local G; G := A247497_row(n); (-1)^(n+1)* add(G[k+1]/(x-1)^(k+1), k=0..n); seq(coeff(series(%, x, len+1),x,j), j=0..len) end: seq(print(col(n,8)), n=0..6); # Peter Luschny, Dec 14 2014

T[0, k_] := If[EvenQ[k], CatalanNumber[k/2], 0];
T[n_, k_] := n^k*Hypergeometric2F1[(1 - k)/2, -k/2, 2, 4/n^2];
Table[T[n - k, k], {n, 0, 10}, {k, n, 0, -1}] // Flatten (* Jean-François Alcover, Nov 03 2017 *)

def A247495(n,k):
    if n==0: return(k//2+1)*factorial(k)/factorial(k//2+1)^2 if is_even(k) else 0
    return n^k*hypergeometric([(1-k)/2,-k/2],[2],4/n^2).simplify()
for n in (0..7): print([A247495(n,k) for k in range(11)])

T(n,k) = (n*(2*k+1)*T(n,k-1)-(n-2)*(n+2)*(k-1)*T(n,k-2))/(k+2) for k>=2.
T(n,k) = Sum_{j=0..floor(k/2)} n^(k-2*j)*binomial(k,2*j)*binomial(2*j,j)/(j+1).
T(n,k) = n^k*hypergeom([(1-k)/2,-k/2], [2], 4/n^2) for n>0.
T(n,n) = A247496(n).
O.g.f. for row n: (1-n*x-sqrt(((n-2)*x-1)*((n+2)*x-1)))/(2*x^2).
O.g.f. for row n: R(x)/x where R(x) is series reversion of x/(1+n*x+x^2).
E.g.f. for row n: exp(n*x)*hypergeom([],[2],x^2).
O.g.f. for column k: the k-th column consists of the values of the k-th Motzkin polynomial M_{k}(x) evaluated at x = 0,1,2,...; M_{k}(x) = sum_{j=0..k} A097610(k,j)*x^j = sum_{j=0..k} (-1)^j*binomial(k,j)*A001006(j)*(x+1)^(k-j).
O.g.f. for column k: sum_{j=0..k} (-1)^(k+1)*A247497(k,j)/(x-1)^(j+1). - Peter Luschny, Dec 14 2014
O.g.f. for row n: 1/(1 - n*x - x^2/(1 - n*x - x^2/(1 - n*x - x^2/(1 - n*x - x^2/(1 - ...))))), a continued fraction. - Ilya Gutkovskiy, Sep 21 2017
T(n,k) is the coefficient of x^k in the expansion of 1/(k+1) * (1 + n*x + x^2)^(k+1). - Seiichi Manyama, May 07 2019

A385728 Expansion of 1/((1-2x) (1-6*x))^(3/2).

Original entry on oeis.org

1, 12, 102, 760, 5310, 35784, 235788, 1530288, 9824310, 62557000, 395797908, 2491381776, 15616141996, 97537784400, 607391245080, 3772617319008, 23379854507046, 144605546475336, 892834113930180, 5504041611527760, 33883431379007364, 208327771987901808

Offset: 0

Seiichi Manyama, Aug 19 2025

Paolo Xausa, Table of n, a(n) for n = 0..1000

Cf. A385563, A385813.

Cf. A005572, A081671, A331515.

R := PowerSeriesRing(Rationals(), 34); f := 1 / ((1 - 2*x) * (1 - 6*x))^(3/2); coeffs := [ Coefficient(f, n) : n in [0..33] ]; coeffs; // Vincenzo Librandi, Aug 22 2025

Module[{a, n}, RecurrenceTable[{a[n] == ((8*n+4)*a[n-1] - 12*(n+1)*a[n-2])/n, a[0] == 1, a[1] == 12}, a, {n, 0, 25}]] (* Paolo Xausa, Aug 21 2025 *)
CoefficientList[Series[ 1/((1-2*x)*(1-6*x))^(3/2),{x,0,33}],x] (* Vincenzo Librandi, Aug 22 2025 *)

my(N=30, x='x+O('x^N)); Vec(1/((1-2*x)*(1-6*x))^(3/2))

n*a(n) = (8*n+4)*a(n-1) - 12*(n+1)*a(n-2) for n > 1.
a(n) = (1/2)^n * Sum_{k=0..n} 3^k * (2*k+1) * (2*(n-k)+1) * binomial(2*k,k) * binomial(2*(n-k),n-k).
a(n) = Sum_{k=0..n} 2^(n-k) * (2*k+1) * binomial(2*k,k) * binomial(n+2,n-k).
a(n) = Sum_{k=0..n} (-1)^k * 6^(n-k) * (2*k+1) * binomial(2*k,k) * binomial(n+2,n-k).
a(n) = binomial(n+2,2) * A005572(n).
a(n) = ((n+2)/2) * Sum_{k=0..floor(n/2)} 4^(n-2*k) * binomial(n+1,n-2*k) * binomial(2*k+1,k).
a(n) = Sum_{k=0..n} 2^k * (-3/2)^(n-k) * (2*k+1) * binomial(2*k,k) * binomial(k,n-k).
a(n) ~ sqrt(n) * 2^(n - 1/2) * 3^(n + 3/2) / sqrt(Pi). - Vaclav Kotesovec, Aug 21 2025

A052177 Number of walks on simple cubic lattice (starting on the xy plane, never going below it and finishing a height 1 above it).

Original entry on oeis.org

0, 1, 8, 50, 288, 1605, 8824, 48286, 264128, 1447338, 7953040, 43842788, 242507456, 1345868589, 7493458392, 41850173670, 234408444288, 1316541032958, 7413214297968, 41842633282620, 236703844320960

Offset: 0

N. J. A. Sloane, Jan 26 2000

Vincenzo Librandi, Table of n, a(n) for n = 0..200
Rigoberto Flórez, Leandro Junes, José L. Ramírez, Further Results on Paths in an n-Dimensional Cubic Lattice, Journal of Integer Sequences, Vol. 21 (2018), Article 18.1.2.
R. K. Guy, Catwalks, sandsteps and Pascal pyramids, J. Integer Sequences, Vol. 3 (2000), Article #00.1.6.

Flatten[{0,RecurrenceTable[{(n-1)*(n+3)*a[n] == 4*n*(2*n+1)*a[n-1] - 12*(n-1)*n*a[n-2],a[1]==1,a[2]==8},a,{n,20}]}] (* Vaclav Kotesovec, Oct 08 2012 *)

a(n) = 4*a(n-1)+A005572(n-1)+A052178(n-1) = A052179(n, 1) = Sum_{j=0..ceiling((n-1)/2)} 4^(n-2j-1)*binomial(n, 2j+1)*binomial(2j+2, j+1)/(j+2).
Recurrence: (n-1)*(n+3)*a(n) = 4*n*(2*n+1)*a(n-1) - 12*(n-1)*n*a(n-2). - Vaclav Kotesovec, Oct 08 2012
a(n) ~ 6^(n+3/2)/(sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 08 2012
G.f.: (1 - 4*x - sqrt(1-8*x+12*x^2))^2/(4*x^3). - Mark van Hoeij, May 16 2013

More terms and formula from Henry Bottomley, Aug 23 2001

A171568 Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A064613.

Original entry on oeis.org

1, 3, 1, 10, 6, 1, 37, 29, 9, 1, 150, 134, 57, 12, 1, 654, 622, 318, 94, 15, 1, 3012, 2948, 1686, 616, 140, 18, 1, 14445, 14317, 8781, 3693, 1055, 195, 21, 1, 71398, 71142, 45625, 21132, 7075, 1662, 259, 24, 1, 361114, 360602, 238170, 118042, 44303, 12345, 2464, 332, 27, 1

Offset: 0

Philippe Deléham, Dec 11 2009

Equal to A171515*B = B*A104259, B = A007318.

			Triangle T(n,k) begins
[0]     1;
[1]     3,     1;
[2]    10,     6,     1;
[3]    37,    29,     9,     1;
[4]   150,   134,    57,    12,    1;
[5]   654,   622,   318,    94,   15,    1;
[6]  3012,  2948,  1686,   616,  140,   18,   1;
[7] 14445, 14317,  8781,  3693, 1055,  195,  21,  1;
[8] 71398, 71142, 45625, 21132, 7075, 1662, 259, 24, 1;
.
Production array begins
  3, 1
  1, 3, 1
  1, 1, 3, 1
  1, 1, 1, 3, 1
  1, 1, 1, 1, 3, 1
  1, 1, 1, 1, 1, 3, 1
- _Philippe Deléham_, Mar 05 2013

Sum_{k=0..n} T(n,k)*x^k = A033543(n), A064613(n), A005572(n), A005573(n) for x = -1, 0, 1, 2 respectively.

Cf. A007318, A052179, A171589, A171515, A104259.

T := proc(n,k) option remember;
if n < 0 or k < 0 then 0 elif n = k then 1 else
T(n-1, k-1) + 3*T(n-1,k) + add(T(n-1, k+1+i), i=0..n) fi end:
for n from 0 to 8 do seq(T(n,k), k = 0..n) od; # Peter Luschny, Oct 16 2022

T[n_, k_] := T[n, k] = If[n < 0 || k < 0, 0, If[n == k, 1, T[n-1, k-1] + 3*T[n-1, k] + Sum[T[n-1, k+1+i], {i, 0, n}]]];
Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Jean-François Alcover, Feb 23 2024, after Peter Luschny *)

T(n, 0) - T(n, 1) = 2^n.

T(n, k) = T(n-1, k-1) + 3*T(n-1, k) + Sum_{i=0..n} T(n-1, k+1+i). - Philippe Deléham, Feb 23 2012

Corrected and extended by Peter Luschny, Oct 16 2022

A302181 Number of 3D walks of type abb.

Original entry on oeis.org

1, 5, 62, 1065, 21714, 492366, 12004740, 308559537, 8255788970, 227976044010, 6457854821340, 186814834574550, 5500292590186380, 164387681345290500, 4976887208815547640, 152378485941172462785, 4711642301137121933850, 146964278352052950118770, 4619875954522866283392300

Offset: 0

N. J. A. Sloane, Apr 09 2018

See Dershowitz (2017) for precise definition.

Nachum Dershowitz, Touchard's Drunkard, Journal of Integer Sequences, Vol. 20 (2017), #17.1.5.

Cf. A000108, A000984, A002212, A002896, A005572, A026375, A064037, A081671, A138547, A145847, A145867, A150500, A202814.

Cf. A005558, A126869.

C := n-> binomial(2*n, n)/(n+1): # Catalan numbers
A302181 := n-> add(binomial(2*n, k)*C(iquo(k+1, 2))*C(iquo(k, 2))*(2*iquo(k, 2)+1)*add((-1)^(k+j)*binomial(2*n-k, iquo(j,2)), j=0..2*n-k), k=0..2*n): seq(A302181(n), n = 0 .. 18); # Mélika Tebni, Nov 06 2024

a(n) = Sum_{k=0..2*n} binomial(2*n, k) * A005558(k) * A126869(2*n-k). - Mélika Tebni, Nov 06 2024

a(8)-a(18) from Nachum Dershowitz, Aug 03 2020

A349318 G.f. A(x) satisfies: A(x) = 1 + x * A(x)^3 / (1 - 2 * x).

Original entry on oeis.org

1, 1, 5, 28, 171, 1113, 7590, 53588, 388519, 2876003, 21648065, 165193576, 1275043280, 9936953788, 78087083456, 618049278976, 4922606097263, 39425205882007, 317316076325015, 2565216211152700, 20819872339143179, 169586043613302169, 1385856599443533442

Offset: 0

Ilya Gutkovskiy, Nov 21 2021

nonn

Cf. A001764, A005572, A307678, A349531, A349532.

nmax = 22; A[] = 0; Do[A[x] = 1 + x A[x]^3/(1 - 2 x) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
a[0] = a[1] = 1; a[n_] := a[n] = 2 a[n - 1] + Sum[Sum[a[i] a[j] a[n - i - j - 1], {j, 0, n - i - 1}], {i, 0, n - 1}]; Table[a[n], {n, 0, 22}]
Table[Sum[Binomial[n - 1, k - 1] Binomial[3 k, k] 2^(n - k)/(2 k + 1), {k, 0, n}], {n, 0, 22}]

a(0) = a(1) = 1; a(n) = 2 * a(n-1) + Sum_{i=0..n-1} Sum_{j=0..n-i-1} a(i) * a(j) * a(n-i-j-1).
a(n) = Sum_{k=0..n} binomial(n-1,k-1) * binomial(3*k,k) * 2^(n-k) / (2*k+1).
a(n) ~ 35^(n + 1/2) / (3 * sqrt(Pi) * n^(3/2) * 2^(2*n + 2)). - Vaclav Kotesovec, Nov 25 2021

A171515 Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A033543.

Original entry on oeis.org

1, 2, 1, 5, 4, 1, 16, 14, 6, 1, 62, 52, 27, 8, 1, 270, 213, 116, 44, 10, 1, 1257, 948, 513, 216, 65, 12, 1, 6096, 4470, 2376, 1038, 360, 90, 14, 1, 30398, 21904, 11468, 5056, 1880, 556, 119, 16, 1

Offset: 0

Philippe Deléham, Dec 10 2009

Equal to B^2*A039598*B^(-2), B = A007318.

			Triangle begins : 1 ; 2,1 : 5,4,1 ; 16,14,6,1 ; 62,52,27,8,1 ; ...

Cf. A052179, A171486

Sum_{k, 0<=k<=n} T(n,k)*x^k = A033543(n), A064613(n), A005572(n), A005573(n) for x = 0, 1, 2, 3 respectively.

T(n,k) = T(n-1,k-1) + 2*T(n-1,k) + sum_{i, i>=0} T(n-1,k+1+i)*2^i. - Philippe Deléham, Feb 23 2012

A272867 Triangle read by rows, T(n,k) = GegenbauerC(m,-n,-2) where m = k if k=0 and 0<=k<=2n.

Original entry on oeis.org

1, 1, 4, 1, 1, 8, 18, 8, 1, 1, 12, 51, 88, 51, 12, 1, 1, 16, 100, 304, 454, 304, 100, 16, 1, 1, 20, 165, 720, 1770, 2424, 1770, 720, 165, 20, 1, 1, 24, 246, 1400, 4815, 10224, 13236, 10224, 4815, 1400, 246, 24, 1

Offset: 0

Peter Luschny, May 08 2016

			                                  1;
                            1,    4,  1;
                         1, 8,   18,  8, 1;
                    1, 12, 51,   88,  51, 12, 1;
              1, 16, 100, 304,  454,  304, 100, 16, 1;
        1, 20, 165, 720, 1770, 2424,  1770, 720, 165, 20, 1;
1, 24, 246, 1400, 4815, 10224, 13236, 10224, 4815, 1400, 246, 24, 1;

Indranil Ghosh, Rows 0..50, flattened

Cf. A005572, A081671.

T := (n,k) -> simplify(GegenbauerC(`if`(k

T[n_, k_]:=If[n<1, 1, If[kIndranil Ghosh, Apr 03 2017 *)

T(n,n) = A081671(n) for n>=0.

T(n+1,n+2)/(n+1) = A005572(n) for n>=0.

A302180 Number of 3D walks of type aad.

Original entry on oeis.org

1, 1, 3, 7, 23, 71, 251, 883, 3305, 12505, 48895, 193755, 783355, 3205931, 13302329, 55764413, 236174933, 1008773269, 4343533967, 18834033443, 82201462251, 360883031291, 1592993944723, 7066748314147, 31493800133173, 140953938878821, 633354801073571, 2856369029213263

Offset: 0

N. J. A. Sloane, Apr 09 2018

See Dershowitz (2017) for precise definition.
Number of 3D walks of length n in the first octant using steps (1, 1, 0), (1, -1, 0), (1, 0, 1), (1, 0, -1) and (1, 0, 0) that start at the origin and end at (n, 0, 0). The analogous problem in 2D is given by the Motzkin numbers A001006. - Farzan Byramji, Mar 06 2021
Inverse binomial transform of A145867 (Number of 3D walks of type aae). - Mélika Tebni, Nov 05 2024

Nachum Dershowitz, Touchard's Drunkard, Journal of Integer Sequences, Vol. 20 (2017), #17.1.5.

Cf. A000108, A000984, A001006, A002212, A002896, A005572, A026375, A064037, A081671, A138547, A145847, A145867, A150500, A202814.

M := n-> add(binomial(n, 2*k)*binomial(2*k, k)/(k+1), k = 0 .. iquo(n,2)): # Motzkin numbers
A302180 := n-> add((-1)^(n-k)*binomial(n, k)*add(binomial(k, j)*M(j)*M(k-j), j=0..k), k=0..n):  seq(A302180(n), n = 0 .. 26); # Mélika Tebni, Nov 05 2024

a(14)-a(26) from Farzan Byramji, Mar 06 2021

cp's OEIS Frontend

A118346 Central terms of pendular triangle A118345.

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A247495 Generalized Motzkin numbers: Square array read by descending antidiagonals, T(n, k) = k!*[x^k](exp(n*x)* BesselI_{1}(2*x)/x), n>=0, k>=0.

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A385728 Expansion of 1/((1-2*x) * (1-6*x))^(3/2).

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A052177 Number of walks on simple cubic lattice (starting on the xy plane, never going below it and finishing a height 1 above it).

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A171568 Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A064613.

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A302181 Number of 3D walks of type abb.

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A349318 G.f. A(x) satisfies: A(x) = 1 + x * A(x)^3 / (1 - 2 * x).

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Mathematica

Formula

A171515 Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A033543.

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A247495 Generalized Motzkin numbers: Square array read by descending antidiagonals, T(n, k) = k![x^k](exp(nx)* BesselI_{1}(2*x)/x), n>=0, k>=0.

A385728 Expansion of 1/((1-2x) (1-6*x))^(3/2).