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 A336227 #5 Jul 13 2020 07:53:26
%S A336227 1,1,4,27,292,4425,89106,2280901,71928872,2728450017,122145511510,
%T A336227 6354868381521,379376236939404,25710543779239501,1960001963705060926,
%U A336227 166753195643254805565,15724259680648667902096,1633462474351643785483457,185931510605274506452763166
%N A336227 a(0) = 1; a(n) = n * Sum_{k=0..n-1} binomial(n-1,k)^2 * a(k).
%F A336227 a(n) = (n!)^2 * [x^n] exp(sqrt(x) * BesselI(1,2*sqrt(x))).
%t A336227 a[0] = 1; a[n_] := a[n] = n Sum[Binomial[n - 1, k]^2 a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 18}]
%t A336227 nmax = 18; CoefficientList[Series[Exp[Sqrt[x] BesselI[1, 2 Sqrt[x]]], {x, 0, nmax}], x] Range[0, nmax]!^2
%Y A336227 Cf. A000248, A023998.
%K A336227 nonn
%O A336227 0,3
%A A336227 _Ilya Gutkovskiy_, Jul 12 2020