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.

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A355619 Square array T(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of e.g.f. (1 + x)^(x^k/k!).

Original entry on oeis.org

1, 1, 1, 1, 0, 0, 1, 0, 2, 0, 1, 0, 0, -3, 0, 1, 0, 0, 3, 20, 0, 1, 0, 0, 0, -6, -90, 0, 1, 0, 0, 0, 4, 20, 594, 0, 1, 0, 0, 0, 0, -10, 0, -4200, 0, 1, 0, 0, 0, 0, 5, 40, -126, 34544, 0, 1, 0, 0, 0, 0, 0, -15, -210, 1260, -316008, 0, 1, 0, 0, 0, 0, 0, 6, 70, 1904, -4320, 3207240, 0
Offset: 0

Views

Author

Seiichi Manyama, Jul 10 2022

Keywords

Examples

			Square array begins:
  1,   1,  1,   1,   1, 1, 1, ...
  1,   0,  0,   0,   0, 0, 0, ...
  0,   2,  0,   0,   0, 0, 0, ...
  0,  -3,  3,   0,   0, 0, 0, ...
  0,  20, -6,   4,   0, 0, 0, ...
  0, -90, 20, -10,   5, 0, 0, ...
  0, 594,  0,  40, -15, 6, 0, ...
		

Crossrefs

Columns k=1..4 give A007113, A355605, (-1)^n * A351493(n), A355603.

Programs

  • PARI
    T(n, k) = n!*sum(j=0, n\(k+1), stirling(n-k*j, j, 1)/(k!^j*(n-k*j)!));

Formula

T(0,k) = 1 and T(n,k) = -(n-1)!/k! * Sum_{j=k+1..n} (-1)^(j-k) * j/(j-k) * T(n-j,k)/(n-j)! for n > 0.
T(n,k) = n! * Sum_{j=0..floor(n/(k+1))} Stirling1(n-k*j,j)/(k!^j * (n-k*j)!).

A355605 Expansion of e.g.f. (1 + x)^(x^2/2).

Original entry on oeis.org

1, 0, 0, 3, -6, 20, 0, -126, 1260, -4320, 5040, 180180, -2601720, 31309200, -372756384, 4877195400, -70178799600, 1099333347840, -18429818232960, 327676010785200, -6146676161388000, 121301442091851840, -2512746856371628800, 54527094987619716000
Offset: 0

Views

Author

Seiichi Manyama, Jul 09 2022

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace((1+x)^(x^2/2)))
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x^2/2*log(1+x))))
    
  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=-(i-1)!/2*sum(j=3, i, (-1)^j*j/(j-2)*v[i-j+1]/(i-j)!)); v;
    
  • PARI
    a(n) = n!*sum(k=0, n\3, stirling(n-2*k, k, 1)/(2^k*(n-2*k)!));

Formula

a(0) = 1; a(n) = -(n-1)!/2 * Sum_{k=3..n} (-1)^k * k/(k-2) * a(n-k)/(n-k)!.
a(n) = n! * Sum_{k=0..floor(n/3)} Stirling1(n-2*k,k)/(2^k * (n-2*k)!).
Showing 1-2 of 2 results.