OFFSET
0,2
FORMULA
G.f.: Product_{k>=1} (1 + 2*(25*x)^k)^(1/5).
a(n) ~ (-1)^(n+1) * QPochhammer(-1/2)^(1/5) * 50^n / (5 * Gamma(4/5) * n^(6/5)).
MATHEMATICA
nmax = 20; CoefficientList[Series[Product[1+2*x^k, {k, 1, nmax}]^(1/5), {x, 0, nmax}], x] * 25^Range[0, nmax]
nmax = 20; CoefficientList[Series[Product[1+2*(25*x)^k, {k, 1, nmax}]^(1/5), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
sign
AUTHOR
Vaclav Kotesovec, Feb 28 2024
STATUS
approved