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) ~ (n^2)! / (n! * ((n-1)!)^n).
a(n) ~ exp(n - 1/12) * n^(n^2 - n/2 + 1/2) / (2*Pi)^(n/2). (End)
PROG
(PARI) {a(n) = sum(k=0, n, (n^2)!/((n^2-n*k)!*k!^n))}
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 29 2019
STATUS
approved