OFFSET
1,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
G.f.: Sum_{k>0} binomial(k-1,3) * x^k/(1 - x^k).
a(n) = Sum_{d|n} binomial(d-1,3).
MATHEMATICA
a[n_] := DivisorSum[n, Binomial[# - 1, 3] &]; Array[a, 50] (* Amiram Eldar, Jul 25 2023 *)
PROG
(PARI) my(N=60, x='x+O('x^N)); concat([0, 0, 0], Vec(sum(k=1, N, x^(4*k)/(1-x^k)^4)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jun 11 2023
STATUS
approved