A321949 Column k=4 of triangle A257673.

1, 12, 78, 376, 1509, 5340, 17234, 51796, 147054, 398388, 1037560, 2612520, 6387965, 15221412, 35446980, 80865304, 181076216, 398660292, 864186408, 1846759404, 3894731430, 8113669352, 16710519860, 34049851236, 68687627812, 137257430140, 271842916654

Offset: 4

Author

Alois P. Heinz, Nov 22 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 4..5000

Crossrefs

Column k=4 of A257673.

Programs

Maple

b:= proc(n, k) option remember; `if`(n=0, 1, k*add(
      b(n-j, k)*numtheory[sigma][2](j), j=1..n)/n)
    end:
a:= n-> (k-> add(b(n, k-i)*(-1)^i*binomial(k, i), i=0..k))(4):
seq(a(n), n=4..35);

Formula

G.f.: (-1 + Product_{k>=1} 1 / (1 - x^k)^k)^4. - Ilya Gutkovskiy, Jan 30 2021