OFFSET
0,10
FORMULA
G.f.: Product_{k>=1} 1 / (1 + (-x)^k)^A046951(k).
MATHEMATICA
nmax = 75; CoefficientList[Series[Product[1/(1 + (-x)^k)^Length[Select[Divisors[k], IntegerQ[Sqrt[#]] &]], {k, 1, nmax}], {x, 0, nmax}], x]
a[n_] := a[n] = If[n == 0, 1, Sum[(-1)^k Sum[(-1)^(k/d) d Length[Select[Divisors[d], IntegerQ[Sqrt[#]] &]], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 75}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 23 2019
STATUS
approved