OFFSET
0,4
COMMENTS
First differences of A026007.
FORMULA
G.f.: (1 - x)*exp(Sum_{k>=1} (-1)^(k+1)*x^k/(k*(1 - x^k)^2)).
a(n) ~ exp(3^(4/3) * Zeta(3)^(1/3) * n^(2/3) / 2^(4/3)) * Zeta(3)^(1/2) / (2^(13/12) * sqrt(Pi) * n). - Vaclav Kotesovec, May 04 2018
MATHEMATICA
nmax = 42; CoefficientList[Series[(1 - x^2) Product[(1 + x^k)^k, {k, 2, nmax}], {x, 0, nmax}], x]
nmax = 42; CoefficientList[Series[(1 - x) Exp[Sum[(-1)^(k + 1) x^k/(k (1 - x^k)^2), {k, 1, nmax}]], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 02 2018
STATUS
approved