OFFSET
1,6
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
G.f.: Sum_{k >= 1} mu(k) * (x/(1 - x^k))^k.
If p is prime, a(p) = 0.
MATHEMATICA
a[n_] := DivisorSum[n, MoebiusMu[#] * Binomial[# + n/# - 2, # - 1] &]; Array[a, 100] (* Amiram Eldar, Apr 22 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, moebius(d)*binomial(d+n/d-2, d-1));
(PARI) my(N=66, x='x+O('x^N)); Vec(sum(k=1, N, moebius(k)*(x/(1-x^k))^k))
CROSSREFS
KEYWORD
sign,look
AUTHOR
Seiichi Manyama, Apr 22 2021
STATUS
approved