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 A168241 #2 Mar 30 2012 18:52:35 %S A168241 1,3,6,10,13,15,19,21,24,27,29,32,35,38,41,43,47,51,54,56,59,61,63,66, %T A168241 69,71,74,76,78,82,85,90,93,96,100,102,104,107,110,114,116,118,121, %U A168241 124,126,129,131,135,137,140,144,146,149,151,153,157,160,163,165,168,171 %N A168241 n-th squarefree number plus n-th non-single or nonisolated number. %F A168241 a(n)=A005117(n)+A167707(n). %K A168241 nonn %O A168241 1,2 %A A168241 _Juri-Stepan Gerasimov_, Nov 21 2009