OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
MAPLE
seq(coeff(series(add(x^k/(1+x^k)^4, k=1..n), x, n+1), x, n), n = 1 .. 45); # Muniru A Asiru, Oct 23 2018
MATHEMATICA
nmax = 44; Rest[CoefficientList[Series[Sum[x^k/(1 + x^k)^4, {k, 1, nmax}], {x, 0, nmax}], x]]
Table[Sum[(-1)^(d + 1) d (d + 1) (d + 2)/6, {d, Divisors[n]}], {n, 44}]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Oct 23 2018
STATUS
approved