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.

A381566 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where column k is the expansion of B(x)^k, where B(x) is the g.f. of A087949.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 3, 2, 0, 1, 4, 6, 6, 5, 0, 1, 5, 10, 13, 15, 16, 0, 1, 6, 15, 24, 33, 46, 59, 0, 1, 7, 21, 40, 63, 99, 164, 246, 0, 1, 8, 28, 62, 110, 188, 343, 662, 1131, 0, 1, 9, 36, 91, 180, 331, 638, 1344, 2961, 5655, 0
Offset: 0

Views

Author

Seiichi Manyama, Feb 28 2025

Keywords

Examples

			Square array begins:
  1,  1,   1,   1,   1,    1,    1, ...
  0,  1,   2,   3,   4,    5,    6, ...
  0,  1,   3,   6,  10,   15,   21, ...
  0,  2,   6,  13,  24,   40,   62, ...
  0,  5,  15,  33,  63,  110,  180, ...
  0, 16,  46,  99, 188,  331,  552, ...
  0, 59, 164, 343, 638, 1110, 1845, ...
		

Crossrefs

Columns k=0..1 give A000007, A087949.

Programs

  • PARI
    a(n, k) = if(k==0, 0^n, k*sum(j=0, n, binomial(n-j+k, j)/(n-j+k)*a(n-j, j)));

Formula

See A087949.

A381568 G.f. A(x) satisfies A(x) = (1 + x*A(x*A(x)))^2.

Original entry on oeis.org

1, 2, 5, 22, 126, 884, 7149, 64688, 641836, 6888740, 79203860, 968503090, 12525131474, 170555767116, 2436592516874, 36409825487380, 567612675812796, 9211031425896752, 155283809480528788, 2714788300934206360, 49140787009610861896, 919625415852055598804, 17768937720619971300781
Offset: 0

Views

Author

Seiichi Manyama, Feb 28 2025

Keywords

Crossrefs

Column k=1 of A381567.

Programs

  • PARI
    a(n, k=1) = if(k==0, 0^n, k*sum(j=0, n, binomial(2*n-2*j+2*k, j)/(n-j+k)*a(n-j, j)));

Formula

See A381567.
G.f.: B(x)^2, where B(x) is the g.f. of A143508.

A381569 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where column k is the expansion of B(x)^k, where B(x) is the g.f. of A381570.

Original entry on oeis.org

1, 1, 0, 1, 3, 0, 1, 6, 12, 0, 1, 9, 33, 82, 0, 1, 12, 63, 236, 732, 0, 1, 15, 102, 489, 2100, 7944, 0, 1, 18, 150, 868, 4428, 22248, 99156, 0, 1, 21, 207, 1400, 8121, 46422, 270268, 1381464, 0, 1, 24, 273, 2112, 13665, 85272, 552540, 3668568, 21065853, 0
Offset: 0

Views

Author

Seiichi Manyama, Feb 28 2025

Keywords

Examples

			Square array begins:
  1,    1,     1,     1,     1,      1, ...
  0,    3,     6,     9,    12,     15, ...
  0,   12,    33,    63,   102,    150, ...
  0,   82,   236,   489,   868,   1400, ...
  0,  732,  2100,  4428,  8121,  13665, ...
  0, 7944, 22248, 46422, 85272, 145143, ...
		

Crossrefs

Columns k=0..1 give A000007, A381570.

Programs

  • PARI
    a(n, k) = if(k==0, 0^n, k*sum(j=0, n, binomial(3*n-3*j+3*k, j)/(n-j+k)*a(n-j, j)));

Formula

A(n,0) = 0^n; A(n,k) = k * Sum_{j=0..n} binomial(3*n-3*j+3*k,j)/(n-j+k) * A(n-j,j).
Showing 1-3 of 3 results.