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 A349966 #21 Dec 08 2021 06:50:13
%S A349966 1,0,1,16,418,17600,1086979,92223488,10292241540,1462309109760,
%T A349966 257739952352133,55188518041440256,14111052911099343782,
%U A349966 4246668467339066589184,1485904567816768099571207,598145009954138900489830400
%N A349966 a(n) = Sum_{k=0..n} (k * (n-k))^n.
%H A349966 Seiichi Manyama, <a href="/A349966/b349966.txt">Table of n, a(n) for n = 0..240</a>
%F A349966 a(n) = [x^n] (Sum_{k=0..n} k^n * x^k)^2.
%F A349966 a(n) ~ sqrt(Pi) * n^(2*n + 1/2) / 2^(2*n + 1). - _Vaclav Kotesovec_, Dec 07 2021
%t A349966 a[0] = 1; a[n_] := Sum[(k*(n - k))^n, {k, 0, n}]; Array[a, 16, 0] (* _Amiram Eldar_, Dec 07 2021 *)
%o A349966 (PARI) a(n) = sum(k=0, n, (k*(n-k))^n);
%Y A349966 Cf. A033455, A100262, A145216, A165817, A306548, A349964, A349965.
%K A349966 nonn
%O A349966 0,4
%A A349966 _Seiichi Manyama_, Dec 07 2021