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 A026253 #4 Mar 30 2012 18:56:05 %S A026253 3,5,1,10,2,15,17,20,22,4,27,29,32,34,6,39,7,44,46,8,51,9,56,58,61,63, %T A026253 11,68,12,73,75,13,80,14,85,87,90,92,16,97,99,102,104,18,109,19,114, %U A026253 116,119,121,21,126,128,131,133,23,138,24,143,145 %N A026253 a(n) = (1/2)*s(n), where s(n) is the n-th even number in A026250. Also a(n) = position of n in A026253. %K A026253 nonn %O A026253 1,1 %A A026253 _Clark Kimberling_