OFFSET
1,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
MATHEMATICA
a[n_] := DivisorSum[n, (-1)^(n/#+1) * (#+n) &] * n/2; Array[a, 55] (* Amiram Eldar, Jul 20 2023 *)
PROG
(PARI) my(N=60, x='x+O('x^N)); Vec(sum(k=1, N, k^2*x^k/(1+x^k)^3))
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jul 19 2023
STATUS
approved