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 A162187 #2 Mar 31 2012 10:31:22 %S A162187 4,24,620448401733239439360000 %N A162187 a(0)=4 and a(n+1)=a(n)! %C A162187 Initializing at 0, 1 or 2 gives constant sequences (except for the first term when initializing at 0). %C A162187 Initializing at 3 gives 3,6,720,720!,... %Y A162187 Cf. A000142 (factorials). %K A162187 bref,nonn %O A162187 0,1 %A A162187 _Benoit Jubin_, Jun 27 2009