OFFSET
0,3
FORMULA
a(n) = [x^n] Product_{k>=1} 1/(1 - x^k/(1 - x)^k)^(k^(n-1)).
MAPLE
seq(coeff(series(mul((1-x^k/(1-x)^k)^(-k^(n-1)), k=1..n), x, n+1), x, n), n = 0 .. 15); # Muniru A Asiru, Oct 15 2018
MATHEMATICA
Table[SeriesCoefficient[Exp[Sum[DivisorSigma[n, k] x^k/(k (1 - x)^k), {k, 1, n}]], {x, 0, n}], {n, 0, 16}]
Table[SeriesCoefficient[Product[1/(1 - x^k/(1 - x)^k)^(k^(n - 1)), {k, 1, n}], {x, 0, n}], {n, 0, 16}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 15 2018
STATUS
approved