OFFSET
1,2
FORMULA
a(n) = Sum_{d|n} (n/d)^(d-1) * binomial(n/d,d-1).
MATHEMATICA
nmax = 50; CoefficientList[Series[Sum[x^k (1 + k x^k)^k, {k, 1, nmax}], {x, 0, nmax}], x] // Rest
Table[DivisorSum[n, (n/#)^(# - 1) Binomial[n/#, # - 1] &], {n, 1, 50}]
PROG
(Magma) [&+[(n div d)^(d-1)*Binomial(n div d, d-1):d in Divisors(n)]:n in [1..50]]; // Marius A. Burtea, Sep 15 2019
(PARI) a(n) = sumdiv(n, d, (n/d)^(d-1) * binomial(n/d, d-1)); \\ Michel Marcus, Sep 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 15 2019
STATUS
approved