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 A166019 #2 Mar 31 2012 13:21:19 %S A166019 1,4,12,28,53,91,141,207,297,401,534,683,869,1081,1327,1601,1912,2275, %T A166019 2665,3095,3569,4110,4682,5314,5996,6744,7535,8394,9320,10303,11367, %U A166019 12490,13686,14938,16288,17707,19227,20808,22490,24233,26103,28033 %N A166019 Right edge of triangular table A138612. %Y A166019 a(n) = A138612(A000217(n)). %K A166019 nonn %O A166019 1,2 %A A166019 _Antti Karttunen_, Oct 05 2009