OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..26
FORMULA
From Vaclav Kotesovec, Jan 29 2019: (Start)
a(n) ~ 2 * (n^2)! / (n!)^n.
a(n) ~ n^(n^2 - n/2 + 1) / (exp(1/12) * 2^((n-3)/2) * Pi^((n-1)/2)). (End)
PROG
(PARI) {a(n) = sum(k=0, n, (n^2)!/((n^2-n*k)!*n!^k))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 29 2019
STATUS
approved