OFFSET
0,4
FORMULA
G.f.: g(g(x) - 1), where g(x) = g.f. of A081362.
MATHEMATICA
nmax = 40; CoefficientList[Series[Product[1/(1 + (-1 + Product[1/(1 + x^k), {k, 1, nmax}])^j), {j, 1, nmax}], {x, 0, nmax}], x]
nmax = 40; CoefficientList[Series[QPochhammer[QPochhammer[x, x^2] - 1, (QPochhammer[x, x^2] - 1)^2], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Apr 08 2019
STATUS
approved