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 A215253 #6 Mar 28 2014 23:43:18 %S A215253 1,2,4,9,18,37,77,150,333,601,1202,2405,4941,9622,21325,38489,76978, %T A215253 153957 %N A215253 a(n) = decimal equivalent of A215254(n). %Y A215253 Cf. A215244-A215246, A215254. %K A215253 nonn,base %O A215253 1,2 %A A215253 _N. J. A. Sloane_, Aug 14 2012