OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..232
FORMULA
E.g.f.: Sum_{k>0} (exp((k * x)^k) - 1).
If p is prime, a(p) = 1 + p^p * p!.
MATHEMATICA
a[n_] := n! * DivisorSum[n, #^n/(n/#)! &]; Array[a, 15] (* Amiram Eldar, Jun 10 2022 *)
PROG
(PARI) a(n) = n!*sumdiv(n, d, d^n/(n/d)!);
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=1, N, exp((k*x)^k)-1)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 10 2022
STATUS
approved