OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..5000
FORMULA
a(n) = Sum_{d|n} (n/d)^d * binomial(n/d+d-2,d-1).
a(p) = p + 1, where p is prime.
MATHEMATICA
nmax = 45; CoefficientList[Series[Sum[k x^k/(1 - k x^k)^k, {k, 1, nmax}], {x, 0, nmax}], x] // Rest
Table[Sum[(n/d)^d Binomial[n/d + d - 2, d - 1], {d, Divisors[n]}], {n, 1, 45}]
PROG
(PARI) a(n) = sumdiv(n, d, (n/d)^d * binomial(n/d+d-2, d-1)); \\ Michel Marcus, Sep 02 2019
(PARI) N=66; x='x+O('x^N); Vec(sum(k=1, N, k*x^k/(1-k*x^k)^k)) \\ Seiichi Manyama, Sep 03 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 02 2019
STATUS
approved