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 A090535 #4 Dec 05 2013 19:56:38 %S A090535 7,17,0,1117,11117,0,1111711,11111117,0,1117111111,17111111111,0, %T A090535 1111171111111,0,0,0,11111111111111171,0,1111111111111111171, %U A090535 11111111111111117111,0,1111111111111111111711,11111111111111111111117 %N A090535 Least n-digit prime using digit 7 once and rest all 1, or 0 if no such prime exists. %C A090535 a(3n) = 0. %e A090535 a(5) = 11117. %Y A090535 Cf. A090536, A090537, A090538. %K A090535 base,nonn %O A090535 1,1 %A A090535 _Amarnath Murthy_, Dec 08 2003 %E A090535 More terms from _David Wasserman_, Jan 03 2006