OFFSET
1,3
FORMULA
a(n) = Sum_{d|n} (-1)^(d-1) * (d+n/d-1)!/(d-1)!.
If p is an odd prime, a(p) = p + p!.
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=1, N, k!*x^k/(1+x^k)^(k+1)))
(PARI) a(n) = sumdiv(n, d, (-1)^(d-1)*(d+n/d-1)!/(d-1)!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 25 2024
STATUS
approved