OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..5000
FORMULA
a(n) = [x^n] Sum_{k>0} (n/k)^(k-1) * x^k / (1 - k * x^k).
If p is prime, a(p) = 2.
MATHEMATICA
a[n_] := DivisorSum[n, #^(n/#-1) * (n/#)^(#-1) &]; Array[a, 40] (* Amiram Eldar, Aug 09 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, d^(n/d-1)*(n/d)^(d-1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 16 2023
STATUS
approved