A326859 E.g.f.: Product_{k>=1} (1 + x^(2*k-1)/(2*k-1)) / (1 - x^(2*k-1)/(2*k-1)).

1, 2, 4, 16, 80, 448, 3136, 24512, 218368, 2169600, 23752704, 282882048, 3661787136, 51076644864, 763127316480, 12184024793088, 206679198990336, 3710945850949632, 70379726872117248, 1405297582300200960, 29462283451103182848, 647386758393297371136

Offset

0,2

Links

Table of n, a(n) for n=0..21.

Formula

a(n) ~ exp(-gamma) * n * n!, where gamma is the Euler-Mascheroni constant A001620.

Mathematica

nmax = 25; CoefficientList[Series[Product[(1+x^(2*k-1)/(2*k-1))/(1-x^(2*k-1)/(2*k-1)), {k, 1, Floor[nmax/2]+1}], {x, 0, nmax}], x] * Range[0, nmax]!

Crossrefs

Cf. A088994, A294506, A305199.

Sequence in context: A027436 A025225 A115125 * A213010 A000831 A000090

Adjacent sequences: A326856 A326857 A326858 * A326860 A326861 A326862

Keyword

nonn

Author

Vaclav Kotesovec, Jul 27 2019

Status

approved