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.

A384029 a(n) = [x^n] Product_{k=0..n-1} (1 + k*x)^4.

Original entry on oeis.org

1, 0, 6, 180, 7206, 370880, 23477380, 1768061064, 154544373158, 15387101825184, 1719596420272980, 213181689525888600, 29036623040055512332, 4310582688852993653568, 692756995680614782818992, 119830419866883597939018000, 22198322332579642585088580870, 4384714751330840129324051474880
Offset: 0

Views

Author

Seiichi Manyama, May 17 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(i=0, n, sum(j=0, 3*n-i, sum(k=0, 3*n-i-j, abs(stirling(n, i, 1)*stirling(n, j, 1)*stirling(n, k, 1)*stirling(n, 3*n-i-j-k, 1)))));

Formula

a(n) = Sum_{0<=i, j, k, l<=n and i+j+k+l=3*n} |Stirling1(n,i) * Stirling1(n,j) * Stirling1(n,k) * Stirling1(n,l)|.

A384026 a(n) = [x^(2*n)] Product_{k=0..n-1} (1 + k*x)^3.

Original entry on oeis.org

1, 0, 0, 8, 1188, 240480, 68630824, 26730127872, 13715719388784, 8994742935058880, 7351374493516431744, 7333037983443263351040, 8772990646534399559904256, 12403600039078715891159873280, 20464777911173655904724421045504, 38976211807455406964301439206318080
Offset: 0

Views

Author

Seiichi Manyama, May 17 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(i=0, n, sum(j=0, n-i, abs(stirling(n, i, 1)*stirling(n, j, 1)*stirling(n, n-i-j, 1))));

Formula

a(n) = Sum_{i, j, k>=0 and i+j+k=n} |Stirling1(n,i) * Stirling1(n,j) * Stirling1(n,k)|.

A384089 a(n) = [x^n] Product_{k=0..n-1} (1 + k*x)^n.

Original entry on oeis.org

1, 0, 1, 63, 7206, 1357300, 384271700, 153027592116, 81648987014364, 56259916067074896, 48646018448463951450, 51584263505394472459750, 65833976467770842558152992, 99553004175105699906002335098, 176031670802373999913671973955080, 359870756416991348769957239299854000
Offset: 0

Views

Author

Seiichi Manyama, May 19 2025

Keywords

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Product[(1 + k*x)^n, {k, 0, n-1}], {x, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, May 19 2025 *)
  • PARI
    a(n) = polcoef(prod(k=0, n-1, 1+k*x)^n, n);

Formula

a(n) = Sum_{0 <= x_1, x_2,..., x_n <= n and x_1 + x_2 + ... + x_n = (n-1)*n} Product_{k=1..n} |Stirling1(n,x_k)|.
a(n) ~ exp(n - 5/3) * n^(2*n+1) / (sqrt(Pi) * n^(3/2) * 2^(n + 1/2)). - Vaclav Kotesovec, May 19 2025
Showing 1-3 of 3 results.