OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..388
FORMULA
G.f.: Sum_{k>=1} mu(k)^2*(k*x)^k/(1 - (k*x)^k).
a(n) = Product_{p|n, p prime} (1 + p^n).
MATHEMATICA
Table[Sum[MoebiusMu[d]^2 d^n, {d, Divisors[n]}], {n, 20}]
nmax = 20; Rest[CoefficientList[Series[Sum[MoebiusMu[k]^2 (k x)^k/(1 - (k x)^k), {k, 1, nmax}], {x, 0, nmax}], x]]
Table[Product[1 + Boole[PrimeQ[d]] d^n, {d, Divisors[n]}], {n, 20}]
PROG
(PARI) a(n) = sumdiv(n, d, moebius(d)^2*d^n) \\ Andrew Howroyd, Nov 06 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 06 2018
STATUS
approved