A127488 a(n) = (n^2)!/(2*(n!)).

6, 30240, 435891456000, 64630041847212441600000, 258328699159653623241666283438080000000

Offset: 2

Author

Artur Jasinski, Jan 16 2007

Keywords

• nonn

Crossrefs

Cf. A000142, A001044, A000442, A036740, A010050, A009445, A134366, A134367, A134368, A134369, A134371, A134372, A134373, A134374, A134374

Programs

Mathematica

Table[(n^2)!/(2(n!)), {n, 2, 6}]

Formula

a(n) ~ n^(2*n^2 - n + 1/2) / (2 * exp(n*(n-1))). - Vaclav Kotesovec, Oct 26 2017