cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 91 results. Next

A174687 Central coefficients T(2n,n) of the Catalan triangle A033184.

Original entry on oeis.org

1, 2, 9, 48, 275, 1638, 9996, 62016, 389367, 2466750, 15737865, 100975680, 650872404, 4211628008, 27341497800, 177996090624, 1161588834303, 7596549816030, 49772989810635, 326658445806000, 2147042307851595, 14130873926790390, 93115841412899760
Offset: 0

Views

Author

Paul Barry, Mar 27 2010

Keywords

Comments

A033184 is the Riordan array (c(x), x*c(x)), c(x) the g.f. of A000108.
Number of standard Young tableaux of shape [2n, n]. Also the number of binary words with 2n 1's and n 0's such that for every prefix the number of 1's is >= the number of 0's. The a(2) = 9 words are: 101011, 101101, 101110, 110011, 110101, 110110, 111001, 111010, 111100. - Alois P. Heinz, Aug 15 2012
Number of lattice paths from (0,0) to (2n,n) not above y=x. - Ran Pan, Apr 08 2015

Crossrefs

Column k=2 of A214776.

Programs

  • Magma
    [(n+1)*Binomial(3*n,n)/(2*n+1): n in [0..25]]; // Vincenzo Librandi, Apr 08 2015
    
  • Maple
    a:= n-> binomial(3*n,n)*(n+1)/(2*n+1):
    seq(a(n), n=0..25);  # Alois P. Heinz, Aug 15 2012
  • Mathematica
    Table[Binomial[3n,n](n+1)/(2n+1), {n, 0, 25}] (* Vincenzo Librandi, Apr 08 2015 *)
  • PARI
    a(n) = (n+1)*binomial(3*n,n)/(2*n+1); \\ Michel Marcus, Nov 12 2022
  • SageMath
    [(n+1)*binomial(3*n,n)/(2*n+1) for n in range(31)] # G. C. Greubel, Nov 09 2022
    

Formula

a(n) = (n+1)*C(3*n, n)/(2n+1) = (n+1)*[x^(n+1)]( Rev(x/c(x)) ) = (n+1)*A001764(n), c(x) the g.f. of A000108.
G.f.: A(x) = sin(arcsin((3^(3/2)*sqrt(x))/2)/3)/(sqrt(3)*sqrt(x)) + cos(arcsin((3^(3/2)* sqrt(x))/2)/3)/(2*sqrt(1-(27*x)/4)). - Vladimir Kruchinin, May 25 2012
2*n*(2*n+1)*a(n) = 3*(13*n^2 -10*n +1)*a(n-1) -9*(3*n-4)*(3*n-5)*a(n-2). - R. J. Mathar, Nov 24 2012
a(n) = [x^n] ((1 - sqrt(1 - 4*x))/(2*x))^(n+1). - Ilya Gutkovskiy, Nov 01 2017
a(n) ~ 3^(3*n+1/2) / (4^(n+1) * sqrt(Pi*n)). - Amiram Eldar, Aug 29 2025

A054445 Triangle read by rows giving partial row sums of triangle A033184(n,m), n >= m >= 1 (Catalan triangle).

Original entry on oeis.org

1, 2, 1, 5, 3, 1, 14, 9, 4, 1, 42, 28, 14, 5, 1, 132, 90, 48, 20, 6, 1, 429, 297, 165, 75, 27, 7, 1, 1430, 1001, 572, 275, 110, 35, 8, 1, 4862, 3432, 2002, 1001, 429, 154, 44, 9, 1, 16796, 11934, 7072, 3640, 1638, 637, 208, 54, 10, 1, 58786, 41990, 25194, 13260
Offset: 0

Views

Author

Wolfdieter Lang, Apr 27 2000 and May 08 2000

Keywords

Comments

In the language of the Shapiro et al. reference (given in A053121) such a lower triangular (ordinary) convolution array, considered as a matrix, belongs to the Riordan-group. The g.f. for the row polynomials p(n,x) (increasing powers of x) is (c(z)^2)/(1-x*z*c(z)) with c(z) = g.f. A000108 (Catalan numbers).
This coincides with the lower triangular Catalan convolution matrix A033184 with first row and first column deleted: a(n,m)= A033184(n+2,m+2), n >= m >= 0, a(n,m) := 0 if n
The Catalan convolution matrix R(n,m) = A033184(n+1,m+1), n >= m >= 0, is the only Riordan-type matrix with R(0,0)=1 whose partial row sums (prs) matrix satisfies (prs(R))(n,m)= R(n+1,m+1), n >= m >= 0.
Riordan array (c(x)^2,x*c(x)) where c(x)is the g.f. of A000108. - Philippe Deléham, Nov 11 2009

Examples

			Triangle starts:
    1;
    2,  1;
    5,  3,  1;
   14,  9,  4,  1;
   42, 28, 14,  5,  1;
  132, 90, 48, 20,  6,  1;
  ...
Fourth row polynomial (n=3): p(3,x)= 14 + 9*x + 4*x^2 + x^3.
Top row of M^3 = [14, 9, 4, 1, 0, 0, 0, ...].
		

Crossrefs

Cf. A033184, A000108. Row sums: a(n+1, 1).

Programs

  • Mathematica
    T[n_, k_] := SeriesCoefficient[((2-2*x)*y)/(2*y+x*Sqrt[1-4*y]-x), {x, 0, n}, {y, 0, k}]; Table[T[n-k+2, k], {n, 0, 10}, {k, n+1, 1, -1}] // Flatten (* Jean-François Alcover, Apr 13 2015, after Vladimir Kruchinin *)
    T[ n_, k_] := (k + 1) Binomial[2 n - k, n] / (n + 1); (* Michael Somos, Oct 01 2018 *)
  • PARI
    tabl(nn) = {
      default(seriesprecision, nn+1);
      my( gf = ((2-2*x)*y)/(2*y+x*sqrt(1-4*y)-x) + O(x^nn) );
      for (n=0, nn-1,  my( P = polcoeff(gf, n, x) );
        for (k=0, nn-1, print1(polcoeff(P, k, y), ", "); );
        print(); );
    } \\ Michel Marcus, Apr 13 2015

Formula

T(n, m) = Sum_{k=m..n} A033184(n+1, k+1), (partial row sums in columns m).
Column m recursion: a(n, m)= sum(a(j-1, m)*A033184(n-j+1, 1), j=m..n) + A033184(n+1, m+1) if n >= m >= 0, a(n, m) := 0 if n
G.f. for column m: (c(x)^2)*(x*c(x))^m, m >= 0, with c(x) = g.f. A000108.
From Gary W. Adamson, Jan 19 2012: (Start)
n-th row of the triangle = top row of M^n, where M is the following infinite square production matrix:
2, 1, 0, 0, 0, ...
1, 1, 1, 0, 0, ...
1, 1, 1, 1, 0, ...
1, 1, 1, 1, 1, ...
...
(End)
G.f.: (((2-2*x)*y)/(2*y+x*sqrt(1-4*y)-x)-1)/(x*y). - Vladimir Kruchinin, Apr 13 2015
T(n, m) = (m+1) * binomial(2*n - m, n) / (n+1) if n>=m>=1. - Michael Somos, Oct 01 2018

A172380 Eigentriangle of Catalan triangle A033184.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 3, 1, 0, 5, 10, 6, 1, 0, 14, 36, 31, 10, 1, 0, 42, 137, 156, 75, 15, 1, 0, 132, 544, 787, 510, 155, 21, 1, 0, 429, 2235, 4017, 3331, 1380, 287, 28, 1, 0, 1430, 9445, 20809, 21405, 11411, 3255, 490, 36, 1, 0, 4862, 40876, 109486, 136921, 90665
Offset: 0

Author

Paul Barry, Feb 01 2010

Keywords

Comments

Row sums are A091768.
Production matrix of inverse is matrix with general term (-1)^(n-k+1)C(k,n-k+1).
Diagonal sums are A172382. Product of A033184 and A172380 is the matrix A172381.

Examples

			Triangle begins
  1;
  0,    1;
  0,    1,    1;
  0,    2,    3,     1;
  0,    5,   10,     6,     1;
  0,   14,   36,    31,    10,     1;
  0,   42,  137,   156,    75,    15,    1;
  0,  132,  544,   787,   510,   155,   21,   1;
  0,  429, 2235,  4017,  3331,  1380,  287,  28,  1;
  0, 1430, 9445, 20809, 21405, 11411, 3255, 490, 36, 1;
Production matrix of inverse is
  0,  1;
  0, -1,  1;
  0,  0, -2,  1;
  0,  0,  1, -3,  1;
  0,  0,  0,  3, -4,   1;
  0,  0,  0, -1,  6,  -5,   1;
  0,  0,  0,  0, -4,  10,  -6,   1;
  0,  0,  0,  0,  1, -10,  15,  -7,   1;
  0,  0,  0,  0,  0,   5, -20,  21,  -8,  1;
  0,  0,  0,  0,  0,  -1,  15, -35,  28, -9,   1;
  0,  0,  0,  0,  0,   0,  -6,  35, -56, 36, -10, 1;
		

A228334 Triangle read by rows: the X-transformation of the Catalan triangle A033184.

Original entry on oeis.org

1, 0, 1, 0, 3, 1, 0, 14, 10, 1, 0, 84, 90, 21, 1, 0, 594, 825, 308, 36, 1, 0, 4719, 7865, 4004, 780, 55, 1, 0, 40898, 78078, 49686, 13650, 1650, 78, 1, 0, 379236, 804440, 606424, 214200, 37400, 3094, 105, 1, 0, 3711916, 8565960, 7379904, 3162816, 724812, 88179, 5320, 136, 1
Offset: 0

Author

N. J. A. Sloane, Aug 26 2013

Keywords

Examples

			Triangle begins:
  1;
  0,   1;
  0,   3,   1;
  0,  14,  10,   1;
  0,  84,  90,  21,   1;
  0, 594, 825, 308,  36,   1;
  ...
		

Crossrefs

Programs

  • Mathematica
    nn = 9;
    c[n_, k_] := Binomial[2n-k, n] (k+1)/(n+1);
    a[0, 0] = 1;
    a[n_, k_] := Table[c[n+k+i-1, 2k+j-1], {i, 1, 2}, {j, 1, 2}] // Det;
    Table[a[n, k], {n, 0, nn}, {k, 0, n}] // Flatten (* Jean-François Alcover, Aug 12 2018 *)
  • PARI
    C(n, k) = (k<=n)*binomial(2*n-k, n)*(k+1)/(n+1);
    aX(nn) = {for (n = 0, nn, for (k = 0, n, print1(matdet(matrix(2, 2, i, j, C(n+k+i-1, 2*k+j-1))), ", ");); print(););} \\ Michel Marcus, Feb 13 2014

Extensions

More terms from Michel Marcus, Feb 13 2014
A-number for Catalan triangle changed by Michel Marcus, Feb 13 2014

A228335 Triangle read by rows: the Y-transformation of the Catalan triangle A033184.

Original entry on oeis.org

1, 1, 1, 3, 6, 1, 14, 40, 15, 1, 84, 300, 175, 28, 1, 594, 2475, 1925, 504, 45, 1, 4719, 22022, 21021, 7644, 1155, 66, 1, 40898, 208208, 231868, 107016, 23100, 2288, 91, 1, 379236, 2068560, 2598960, 1439424, 403920, 58344, 4095, 120, 1, 3711916, 21414900, 29651400, 18976896, 6523308, 1247103, 129675, 6800, 153, 1
Offset: 0

Author

N. J. A. Sloane, Aug 26 2013

Keywords

Comments

From Roger Ford, Feb 08 2020: (Start)
For 2n-step octant walks, the numbers for the x axis ending locations are equal to numbers in row n of the example triangle.
Example: For n = 2, all 4-step octant walks starting at (0,0) and ending on the x axis are as follows:
EWEW EEWW EEEW EWEE EEWE EEEE
ENSW EENS ENSE ENES
(0,0) (2,0) (4,0) - x axis ending location
3 6 1 - number of walks
These numbers match row 2 of the example triangle. (End)

Examples

			Triangle begins:
    1;
    1,    1;
    3,    6,    1;
   14,   40,   15,    1;
   84,  300,  175,   28,    1;
  594, 2475, 1925,  504,   45,    1;
  ...
		

Crossrefs

Programs

  • Mathematica
    nn = 9;
    c[n_, k_] := Binomial[2n-k, n] (k+1)/(n+1);
    a[0, 0] = 1;
    a[n_, k_] := Table[c[n+k+i, 2k+j], {i, 2}, {j, 2}] // Det;
    Table[a[n, k], {n, 0, nn}, {k, 0, n}] // Flatten (* Jean-François Alcover, Aug 12 2018 *)
  • PARI
    C(n, k) = (k<=n)*binomial(2*n-k, n)*(k+1)/(n+1);
    T(n, k) = matdet(matrix(2, 2, i, j, C(n+k+i, 2*k+j))); \\ Michel Marcus, Feb 13 2014

Extensions

More terms from Michel Marcus, Feb 13 2014
A-number for Catalan triangle changed by Michel Marcus, Feb 13 2014

A228336 Triangle read by rows: the Z-transformation of the Catalan triangle A033184.

Original entry on oeis.org

1, 1, 1, 2, 2, 1, 4, 6, 3, 1, 10, 15, 12, 4, 1, 25, 45, 36, 20, 5, 1, 70, 126, 126, 70, 30, 6, 1, 196, 392, 392, 280, 120, 42, 7, 1, 588, 1176, 1344, 960, 540, 189, 56, 8, 1, 1764, 3780, 4320, 3600, 2025, 945, 280, 72, 9, 1, 5544, 11880, 14850, 12375, 8250, 3850, 1540, 396, 90, 10, 1
Offset: 0

Author

N. J. A. Sloane, Aug 26 2013

Keywords

Examples

			Triangle begins:
   1;
   1,   1;
   2,   2,   1;
   4,   6,   3,  1;
  10,  15,  12,  4,  1;
  25,  45,  36, 20,  5, 1;
  70, 126, 126, 70, 30, 6, 1;
  ...
		

Crossrefs

Programs

  • Mathematica
    c[n_, k_] := Boole[k <= n] Binomial[2n - k, n] (k + 1)/(n + 1);
    T[n_, k_] := Module[{nn, kk}, If[OddQ[n], nn = (n + 1)/2, nn = n/2]; If[OddQ[k], kk = (k - 1)/2, kk = k/2]; If [OddQ[n], If[OddQ[k], c[nn + kk, 2kk + 1] c[nn + kk + 1, 2kk + 2], c[nn + kk, 2kk] c[nn + kk, 2kk + 1]], If[OddQ[k], c[nn + kk + 1, 2kk + 1] c[nn + kk + 1, 2kk + 2], c[nn + kk, 2kk] c[nn + kk + 1, 2kk + 1]]]];
    Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Oct 04 2018, from PARI *)
  • PARI
    C(n, k) = (k<=n)*binomial(2*n-k, n)*(k+1)/(n+1);
    T(n, k) = {my(nn, kk); if (n % 2, nn = (n+1)/2, nn = n/2); if (k % 2, kk = (k-1)/2, kk = k/2); if ((n % 2), if (k % 2, C(nn+kk, 2*kk+1)*C(nn+kk+1, 2*kk+2), C(nn+kk, 2*kk)*C(nn+kk, 2*kk+1)), if (k % 2, C(nn+kk+1, 2*kk+1)*C(nn+kk+1, 2*kk+2), C(nn+kk, 2*kk)*C(nn+kk+1, 2*kk+1)));} \\ Michel Marcus, Feb 13 2014

Extensions

More terms from Michel Marcus, Feb 13 2014
A-number for Catalan triangle changed by Michel Marcus, Feb 13 2014

A228337 Irregular triangle read by rows: the W-transformation of the Catalan triangle A033184.

Original entry on oeis.org

1, 2, 4, 1, 10, 4, 20, 21, 1, 56, 70, 6, 140, 238, 50, 1, 420, 792, 210, 8, 1176, 2604, 990, 91, 1, 3696, 8778, 3850, 462, 10, 11088, 29106, 15675, 2772, 144, 1, 36036, 99528, 59202, 12376, 858, 12, 113256, 335049, 228085, 60060, 6240, 209, 1
Offset: 0

Author

N. J. A. Sloane, Aug 26 2013

Keywords

Examples

			Triangle begins:
     1;
     2;
     4,    1;
    10,    4;
    20,   21,    1;
    56,   70,    6;
   140,  238,   50,    1;
   420,  792,  210,    8;
  1176, 2604,  990,   91,    1;
  ...
		

Crossrefs

Programs

  • Mathematica
    nn = 12;
    c[n_, k_] := If[k <= n, Binomial[2n-k, n] (k+1)/(n+1), 0];
    a[n_, k_] := Table[c[If[OddQ[n], (n-1)/2+k+2i-2, n/2+k+i-1], 2k+j-1], {i, 1, 2}, {j, 1, 2}] // Permanent;
    Table[a[n, k], {n, 0, nn}, {k, 0, n/2}] // Flatten (* Jean-François Alcover, Aug 12 2018 *)
  • PARI
    C(n, k) = (k<=n)*binomial(2*n-k, n)*(k+1)/(n+1);
    matperm(M)=my(n=#M,t);sum(i=1,n!,t=numtoperm(n,i);prod(j=1,n,M[j,t[j]])); \\ from Rosetta code
    W(n, k) = my(nn); if (n % 2, nn = (n-1)/2; matperm(matrix(2, 2, i, j, C(nn+k+2*i-2, 2*k+j-1))), nn = n/2; matperm(matrix(2, 2, i, j, C(nn+k+i-1, 2*k+j-1))));
    aW(nn) = {for (n=0, nn, for (k=0, n\2, print1(W(n, k), ", ");); print(););} \\ Michel Marcus, Feb 13 2014

Extensions

More terms from Michel Marcus, Feb 13 2014
A-number for Catalan triangle changed by Michel Marcus, Feb 13 2014

A116363 a(n) = dot product of row n in Catalan triangle A033184 with row n in Pascal's triangle.

Original entry on oeis.org

1, 2, 7, 30, 141, 698, 3571, 18686, 99385, 535122, 2908863, 15932766, 87809541, 486421770, 2706138987, 15110359038, 84637982961, 475381503266, 2676447372535, 15100548901790, 85357620588541, 483304834607322
Offset: 0

Author

Paul D. Hanna, Feb 04 2006

Keywords

Examples

			The dot product of Catalan row 4 and Pascal row 4 equals a(4) = [14,14,9,4,1]*[1,4,6,4,1] = 141
which is equivalent to obtaining the final term in these repeated partial sums of Pascal row 4:
  1,4, 6, 4, 1
   5,11,15,16
    16,31,47
     47,94
      141
		

Crossrefs

Cf. A033184.

Programs

  • GAP
    List([0..30], n-> Sum([0..n], j-> Binomial(n,j)*Binomial(2*n-j+1, n-j)*(j+1)/(2*n-j+1))); # G. C. Greubel, May 12 2019
  • Magma
    [(&+[Binomial(n,j)*Binomial(2*n-j+1, n-j)*(j+1)/(2*n-j+1): j in [0..n]]): n in [0..30]]; // G. C. Greubel, May 12 2019
    
  • Mathematica
    Table[Sum[Binomial[n, j]*Binomial[2*n-j+1, n-j]*(j+1)/(2*n-j+1), {j,0,n} ], {n,0,30}] (* G. C. Greubel, May 12 2019 *)
  • PARI
    a(n)=sum(k=0,n,binomial(n,k)*binomial(2*n-k+1,n-k)*(k+1)/(2*n-k+1))
    for(n=0,30,print1(a(n),", "))
    
  • Sage
    [sum(binomial(n,j)*binomial(2*n-j+1, n-j)*(j+1)/(2*n-j+1) for j in (0..n)) for n in (0..30)] # G. C. Greubel, May 12 2019
    

Formula

a(n) = Sum_{k=0..n} C(n,k)*C(2*n-k+1,n-k)*(k+1)/(2*n-k+1).
G.f. A(x) satisfies: d/dx[log(1 - 4*x*A(x))] = -4*(1-5*x)/(1-13*x+43*x^2-7*x^3).
O.g.f.: 2*(R+x)/(R*(R+x+1)), where R = sqrt(x^2+6*x+1). [Dan Drake, May 19 2010]
Conjecture: +(2*n+5)*(n+1)*a(n) +4*(-3*n^2-9*n+5)*a(n-1) +(2*n+7)*(n-1)*a(n-2)=0. - R. J. Mathar, Jun 22 2016

A116364 Row squared sums of Catalan triangle A033184.

Original entry on oeis.org

1, 2, 9, 60, 490, 4534, 45689, 489920, 5508000, 64276492, 773029466, 9531003552, 119990158054, 1537695160070, 20009930706137, 263883333450760, 3521003563829212, 47470845904561648, 645960472314074400
Offset: 0

Author

Paul D. Hanna, Feb 04 2006

Keywords

Comments

Number of 321-avoiding permutations in which the length of the longest increasing subsequence is n. Example: a(2)=9 because we have 12, 132, 312, 213, 231, 3142, 3412, 2143 and 2413. Column sums of triangle in A126217 (n >= 1). - Emeric Deutsch, Sep 07 2007

Examples

			The dot product of Catalan row 4 with itself equals
  a(4) = [14,14,9,4,1]*[14,14,9,4,1] = 490
which is equivalent to obtaining the final term in these repeated partial sums of Catalan row 4:
  14,   14,    9,    4,    1
     28,   37,   41,   42
        65,  106,  148
          171,  319
             490
		

Crossrefs

Programs

  • GAP
    List([0..30], n-> Sum([0..n], j-> (Binomial(2*n-j+1, n-j)* (j+1)/(2*n-j+1))^2 )); # G. C. Greubel, May 12 2019
  • Magma
    [(&+[(Binomial(2*n-j+1, n-j)*(j+1)/(2*n-j+1))^2: j in [0..n]]): n in [0..30]]; // G. C. Greubel, May 12 2019
    
  • Maple
    a:=proc(k) options operator, arrow: sum((2*k-n+1)^2*binomial(n+1,k+1)^2/(n+1)^2,n=k..2*k) end proc: 1,seq(a(k),k=1..17); # Emeric Deutsch, Sep 07 2007
  • Mathematica
    Table[Sum[(Binomial[2*n-j+1, n-j]*(j+1)/(2*n-j+1))^2, {j, 0, n}], {n, 0, 30}] (* G. C. Greubel, May 12 2019 *)
  • PARI
    a(n)=sum(k=0,n,((k+1)*binomial(2*n-k+1,n-k)/(2*n-k+1))^2)
    
  • Sage
    [sum(( binomial(2*n-j+1, n-j)*(j+1)/(2*n-j+1) )^2 for j in (0..n)) for n in (0..30)] # G. C. Greubel, May 12 2019
    

Formula

a(n) = Sum_{k=0..n} (C(2*n-k+1,n-k)*(k+1)/(2*n-k+1))^2.

A127742 Triangle read by rows with shape A000041 which refines the Catalan triangle A033184 using sequence A048996.

Original entry on oeis.org

1, 1, 1, 2, 2, 1, 5, 4, 1, 3, 1, 14, 10, 4, 6, 3, 4, 1, 42, 28, 10, 4, 15, 12, 1, 8, 6, 5, 1, 132, 84, 28, 20, 42, 30, 12, 6, 20, 24, 4, 10, 10, 6, 1, 429, 264, 84, 56, 25, 126, 84, 60, 15, 12, 56, 60, 24, 24, 1, 25, 40, 10, 12, 15, 7, 1, 1430, 858, 264, 168, 140, 396, 252, 168, 75
Offset: 1

Author

Alford Arnold, Feb 23 2007

Keywords

Comments

Contribution from R. J. Mathar, Jul 16 2010: (Start)
The entries count Dyck paths of length 2n which have a step/stride pattern between consecutive returns to the horizontal axes (after sorting) equivalent to the k-th partition of n.
Equivalent means that each distance between two x (where y=0) is divided by 2 prior to comparison.
Example: if the x-values are (0,4,8,10,16) with 2n=16, the strides are 4,4,2,6, equal to 2,2,1,3 after division by 2, and contribute to the 1^1,2^2,3^1 partition T(8,14). (End)

Examples

			The triangle begins
1
1 1
2 2 1
5 4 1 3 1
14 10 4 6 3 4 1
etc
		

Extensions

More terms from R. J. Mathar, Jul 16 2010
Showing 1-10 of 91 results. Next