OFFSET
1,2
FORMULA
a(n) = [x^n] Sum_{k>0} (1/(1 - (k*x)^k)^n - 1).
MATHEMATICA
a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + n - 1, #] &]; Array[a, 20] (* Amiram Eldar, Jul 12 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (n/d)^n*binomial(d+n-1, d));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 14 2023
STATUS
approved