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 A014890 #5 Mar 30 2012 17:28:13 %S A014890 1,421,422,423,424,425,426,432,433,1726,3888,3889,4309,4310,4311,4312, %T A014890 4313,4314,4320,4321,9330 %N A014890 n is equal to the number of 1's in all numbers <= n written in base 6. %Y A014890 Cf. A014778. %K A014890 nonn,base,fini,full %O A014890 1,2 %A A014890 _Olivier Gérard_ %E A014890 List proved complete by _Hugo van der Sanden_ (cf. A014886).