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 A342196 #5 Mar 04 2021 20:55:45
%S A342196 1,1,5,23,155,1355,14371,183911,2781283,48726355,976903875,
%T A342196 22183097191,565060532965,16016170519017,501714014484813,
%U A342196 17265124180702953,649178961366102597,26544344366333824055,1175291769917975444817,56133021061270139242637,2881893164859601701738005
%N A342196 a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k)^2 * a(k-1).
%t A342196 a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k]^2 a[k - 1], {k, 1, n}]; Table[a[n], {n, 0, 20}]
%Y A342196 Cf. A023998, A040027, A101514, A102221, A342197, A342198, A342199.
%K A342196 nonn
%O A342196 0,3
%A A342196 _Ilya Gutkovskiy_, Mar 04 2021