OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..719
FORMULA
G.f.: Sum_{k >= 1} (tau(k) * x)^k/(1 - (tau(k) * x)^k).
If p is prime, a(p) = 1 + 2^p.
MATHEMATICA
a[n_] := DivisorSum[n, DivisorSigma[0, #]^n &]; Array[a, 26] (* Amiram Eldar, May 09 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, numdiv(d)^n);
(PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=1, N, (numdiv(k)*x)^k/(1-(numdiv(k)*x)^k)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 09 2021
STATUS
approved