OFFSET
1,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
a[n_] := DivisorSum[n, (-1)^# * Binomial[# + 1, 3] &]; Array[a, 50] (* Amiram Eldar, Jul 25 2023 *)
PROG
(PARI) my(N=50, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(2*k)/(1+x^k)^4)))
(PARI) a(n) = sumdiv(n, d, (-1)^d*binomial(d+1, 3));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jun 11 2023
STATUS
approved