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 A247001 #3 Sep 21 2014 14:09:15 %S A247001 1,5,21,85,317,1157 %N A247001 A246335(2^n-1). %C A247001 Mysteriously different from A002450. %Y A247001 Cf. A246333, A246334, A246335, A002450. %K A247001 nonn,more %O A247001 0,2 %A A247001 _N. J. A. Sloane_, Sep 21 2014