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 A173818 #4 Mar 30 2012 18:52:39 %S A173818 1,2,4,6,38,66,398,1260,3980 %N A173818 3*n-1 is a circular prime. %Y A173818 Cf. A016114. %K A173818 nonn,less %O A173818 1,2 %A A173818 _Juri-Stepan Gerasimov_, Feb 25 2010