OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..500
FORMULA
a(n) = [x^n] Product_{k_1>=1, k_2>=1, ..., k_n>=1} (1 + x^(k_1*k_2*...*k_n)).
MATHEMATICA
tau[n_, 1] = 1; tau[n_, k_] := tau[n, k] = Plus @@ (tau[#, k-1] & /@ Divisors[n]); nmax = 30; Table[SeriesCoefficient[Product[(1 + x^k)^tau[k, n], {k, 1, n}], {x, 0, n}], {n, 0, nmax}] (* Vaclav Kotesovec, Oct 29 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 29 2018
STATUS
approved