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 A368838 #9 Jan 09 2024 12:40:31
%S A368838 1,5,51,919,25733,1029321,55583335,3890833451,342393343689,
%T A368838 36978481118413,4807202545393691,740309191990628415,
%U A368838 133255654558313114701,27717176148129127857809,6596687923254732430158543,1781105739278777756142806611,541456144740748437867413209745
%N A368838 a(n) = n! * (n+3)! * Sum_{k=0..n} 1/(k! * (k+3)!).
%F A368838 a(n) = n*(n+3)*a(n-1) + 1.
%F A368838 a(n) ~ BesselI(3,2) * n! * (n+3)!. - _Vaclav Kotesovec_, Jan 09 2024
%o A368838 (PARI) a(n) = n!*(n+3)!*sum(k=0, n, 1/(k!*(k+3)!));
%Y A368838 Cf. A099597, A006040, A228229, A368837.
%K A368838 nonn,easy
%O A368838 0,2
%A A368838 _Seiichi Manyama_, Jan 07 2024