This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A306207 #16 Jan 30 2019 06:21:19
%S A306207 1,2,19,9745,768211081,17406784944114721,179762725526880242306609281,
%T A306207 1230064011299573560897489169488350806401,
%U A306207 7660929590740297929124296619236388608530015362840364161
%N A306207 a(n) = Sum_{k=0..n} (n^2)!/((n^2-n*k)!*k!^n).
%H A306207 Seiichi Manyama, <a href="/A306207/b306207.txt">Table of n, a(n) for n = 0..26</a>
%F A306207 From _Vaclav Kotesovec_, Jan 29 2019: (Start)
%F A306207 a(n) ~ (n^2)! / (n! * ((n-1)!)^n).
%F A306207 a(n) ~ exp(n - 1/12) * n^(n^2 - n/2 + 1/2) / (2*Pi)^(n/2). (End)
%o A306207 (PARI) {a(n) = sum(k=0, n, (n^2)!/((n^2-n*k)!*k!^n))}
%Y A306207 Cf. A206849, A227403, A306206.
%K A306207 nonn
%O A306207 0,2
%A A306207 _Seiichi Manyama_, Jan 29 2019