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 A166018 #2 Mar 31 2012 13:21:19 %S A166018 1,2,3,5,6,8,9,10,13,14,16,17,18,21,22,24,25,29,30,31,32,34,36,38,40, %T A166018 41,44,45,47,48,51,54,55,56,58,59,62,63,65,67,69,72,73,74,75,77,80,81, %U A166018 83,84,87,89,92,94,96,98,99,100,102,103,104,109,110,111,113,116,118 %N A166018 Left edge of triangular table A138612. %F A166018 a(n) = A138612(A000124(n-1)). %K A166018 nonn %O A166018 1,2 %A A166018 _Antti Karttunen_, Oct 05 2009