OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = Sum_{d|n} mu(n/d) * binomial(d+n-1, n).
a(n) = [x^n] Sum_{k>=1} mu(k) * x^k/(1 - x^k)^(n+1).
MATHEMATICA
a[n_] := DivisorSum[n, MoebiusMu[n/#] * Binomial[# + n - 1, n] &]; Array[a, 30] (* Amiram Eldar, Apr 25 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, moebius(n/d)*binomial(d+n-1, n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 20 2021
STATUS
approved