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A371548
Expansion of e.g.f. Product_{k>=1} (1 + 2*x^k/k).
1
1, 2, 2, 16, 44, 248, 2136, 13536, 116448, 1075392, 13066560, 136385280, 1811975040, 23777683200, 354509003520, 5632664970240, 93712140103680, 1631567291719680, 30968760551178240, 605247894280028160, 12515132360676556800, 274444506310599475200
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