OFFSET
0,2
FORMULA
a(n) ~ n! * n / (2*exp(2*gamma)), where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, Mar 28 2024
MATHEMATICA
nmax = 21; CoefficientList[Series[Product[(1 + 2 x^k/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 27 2024
STATUS
approved