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 A368837 #10 Jan 09 2024 12:38:53
%S A368837 1,4,33,496,11905,416676,20000449,1260028288,100802263041,
%T A368837 9979424041060,1197530884927201,171246916544589744,
%U A368837 28769481979491076993,5610048986000760013636,1256650972864170243054465,320445998080363411978888576
%N A368837 a(n) = n! * (n+2)! * Sum_{k=0..n} 1/(k! * (k+2)!).
%F A368837 a(n) = n*(n+2)*a(n-1) + 1.
%F A368837 a(n) ~ BesselI(2,2) * n! * (n+2)!. - _Vaclav Kotesovec_, Jan 09 2024
%o A368837 (PARI) a(n) = n!*(n+2)!*sum(k=0, n, 1/(k!*(k+2)!));
%Y A368837 Cf. A099597, A006040, A228229, A368838.
%K A368837 nonn,easy
%O A368837 0,2
%A A368837 _Seiichi Manyama_, Jan 07 2024