OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..388
FORMULA
L.g.f.: -log(Product_{k>=1} (1 - (k*x)^k)^(1/k^3)) = Sum_{k>=1} a(k)*x^k/k.
G.f.: Sum_{k>=1} k^(k-2) * x^k/(1 - (k*x)^k).
MATHEMATICA
a[n_] := DivisorSum[n, #^(n - 2) &]; Array[a, 20] (* Amiram Eldar, May 08 2021 *)
PROG
(PARI) {a(n) = sigma(n, n-2)}
(PARI) N=20; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-(k*x)^k)^(1/k^3)))))
(PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, k^(k-2)*x^k/(1-(k*x)^k)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 23 2019
STATUS
approved