A321954 Column k=9 of triangle A257673.

1, 27, 378, 3681, 28134, 180198, 1007370, 5051790, 23173047, 98644395, 394006761, 1489460724, 5365964511, 18526724685, 61587671283, 197885754837, 616568620176, 1868127089697, 5517376711191, 15917134652829, 44935916034951, 124340811582540, 337706753653476

Offset: 9

Author

Alois P. Heinz, Nov 22 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 9..5000

Crossrefs

Column k=9 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))(9):
seq(a(n), n=9..35);

Formula

G.f.: (-1 + Product_{k>=1} 1 / (1 - x^k)^k)^9. - Ilya Gutkovskiy, Jan 31 2021