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 A024763 #5 Mar 30 2012 18:35:23 %S A024763 2,21,212,2122 %N A024763 Every prefix prime in base 3 (written in base 3). %K A024763 nonn,base,fini,full %O A024763 1,1 %A A024763 _David W. Wilson_