OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..337
FORMULA
From Vaclav Kotesovec, Feb 08 2019: (Start)
a(n) ~ exp(1) * A135860(n).
a(n) ~ exp(n + 3/2) * n^(n - 1/2) / sqrt(2*Pi). (End)
MATHEMATICA
a[n_] := Sum[Binomial[n, k] * Binomial[n^2+k, k], {k, 0, n}]; Array[a, 20, 0] (* Amiram Eldar, Feb 03 2019 *)
PROG
(PARI) {a(n) = sum(k=0, n, binomial(n, k)*binomial(n^2+k, k))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 02 2019
STATUS
approved