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 A138713 #2 Mar 30 2012 17:33:54 %S A138713 11,11000,1100011111,11000111110000000,1100011111000000011111111111, %T A138713 11000111110000000111111111110000000000000, %U A138713 1100011111000000011111111111000000000000011111111111111111 %N A138713 Concatenation of first n runs of A138149 (related to prime numbers). %Y A138713 Cf. A000040, A138149. %K A138713 base,easy,nonn %O A138713 1,1 %A A138713 _Omar E. Pol_, Mar 29 2008