A352839 Expansion of g.f. 1/(1 - Sum_{k>=1} sigma_k(k) * x^k).

1, 1, 6, 39, 370, 4132, 59288, 990705, 19577018, 439550259, 11142216938, 313147651821, 9680830606850, 325944181383936, 11875777329091878, 465292113335910106, 19507503314546762246, 871248546067010133794, 41295079536653463057146

Offset: 0

Author

Seiichi Manyama, Apr 05 2022

Keywords

• nonn

Crossrefs

Cf. A129921, A180305, A320649.

Cf. A023887, A352841, A352842.

Programs

PARI

my(N=20, x='x+O('x^N)); Vec(1/(1-sum(k=1, N, sigma(k, k)*x^k)))

PARI

a(n) = if(n==0, 1, sum(k=1, n, sigma(k, k)*a(n-k)));

Formula

a(0) = 1; a(n) = Sum_{k=1..n} sigma_k(k) * a(n-k).