OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..214
FORMULA
L.g.f.: -log(Product_{k>=1} (1 - (k^2*x)^k)^(1/k)) = Sum_{k>=1} a(k)*x^k/k.
a(n) ~ n^(2*n). - Vaclav Kotesovec, Jun 08 2019
MATHEMATICA
Table[DivisorSigma[2 n, n], {n, 1, 20}] (* Vaclav Kotesovec, Jun 08 2019 *)
PROG
(PARI) {a(n) = sigma(n, 2*n)}
(PARI) N=20; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-(k^2*x)^k)^(1/k)))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 08 2019
STATUS
approved