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 A005604 #12 Jul 08 2025 00:26:36
%S A005604 1,1,2,3,8,40326
%N A005604 a(n) = a(n-1)! + a(n-2)!.
%C A005604 The next term has 168215 decimal digits. - _Rick L. Shepherd_, Nov 04 2004
%t A005604 nxt[{a_,b_}]:={b,a!+b!}; NestList[nxt,{1,1},5][[All,1]] (* _Harvey P. Dale_, Aug 12 2020 *)
%Y A005604 A114020 is an essentially identical sequence.
%K A005604 nonn,easy
%O A005604 0,3
%A A005604 _N. J. A. Sloane_