OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = Sum_{d|n} (n/d)^d * binomial(n/d,d).
a(p) = p^2, where p is prime.
MATHEMATICA
nmax = 43; CoefficientList[Series[Sum[((1 + k x^k)^k - 1), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
Table[DivisorSum[n, (n/#)^# Binomial[n/#, #] &], {n, 1, 43}]
PROG
(PARI) a(n)={sumdiv(n, d, (n/d)^d * binomial(n/d, d))} \\ Andrew Howroyd, Sep 14 2019
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Ilya Gutkovskiy, Sep 14 2019
STATUS
approved