OFFSET
1,2
FORMULA
G.f.: Sum_{k>=1} x^k/(1 - (k * x)^k)^2.
If p is prime, a(p) = 1 + p.
MATHEMATICA
a[n_] := DivisorSum[n, #^(n-#)*n/# &]; Array[a, 29] (* Amiram Eldar, Aug 27 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, n/d*d^(n-d));
(PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=1, N, x^k/(1-(k*x)^k)^2))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Dec 17 2022
STATUS
approved