OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..388
FORMULA
If p is prime, a(p) = -1 - p^p.
MATHEMATICA
a[n_] := DivisorSum[n, MoebiusMu[#] * MoebiusMu[n/#] * #^n &]; Array[a, 20] (* Amiram Eldar, Aug 24 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, moebius(d)*moebius(n/d)*d^n);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Aug 24 2021
STATUS
approved