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 1-3 of 3 results.

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

Views

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

Views

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

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

Views

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
Showing 1-3 of 3 results.