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 A162185 #4 Apr 01 2018 13:41:20 %S A162185 3,8,256, %T A162185 115792089237316195423570985008687907853269984665640564039457584007913129639936 %N A162185 a(0)=3 and a(n+1)=2^a(n). %C A162185 Initializing at 0, 1, 2 or 4 gives A014221. %t A162185 NestList[2^#&,3,3] (* _Harvey P. Dale_, Apr 01 2018 *) %Y A162185 A000079 (powers of 2). %K A162185 nonn %O A162185 0,1 %A A162185 _Benoit Jubin_, Jun 27 2009