OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..447
FORMULA
E.g.f.: Sum_{k>0} (1 - exp(-k * x^k)).
If p is prime, a(p) = (-1)^(p+1) + p * p!.
MATHEMATICA
a[n_] := -n! * DivisorSum[n, (-n/#)^#/#! &]; Array[a, 20] (* Amiram Eldar, Jul 03 2023 *)
PROG
(PARI) a(n) = -n!*sumdiv(n, d, (-n/d)^d/d!);
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Jun 16 2023
STATUS
proposed