OFFSET
0,4
COMMENTS
Weigh transform of A001227.
FORMULA
G.f.: Product_{k>=1} (1 + x^k)^A001227(k).
MATHEMATICA
nmax = 47; CoefficientList[Series[Product[(1 + x^k)^DivisorSum[k, Mod[#, 2] &], {k, 1, nmax}], {x, 0, nmax}], x]
a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d DivisorSum[d, Mod[#, 2] &], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 47}]
PROG
(PARI) seq(n)={Vec(prod(k=1, n, (1 + x^k + O(x*x^n))^numdiv(k>>valuation(k, 2))))} \\ Andrew Howroyd, Sep 23 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 23 2019
STATUS
approved