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 A026257 #4 Mar 30 2012 18:56:05 %S A026257 1,2,4,5,3,6,11,12,7,8,9,17,18,10,19,24,13,25,14,15,16,30,31,32,37,20, %T A026257 38,21,22,23,43,44,45,26,49,50,27,51,28,29,56,57,58,33,62,63,34,64,35, %U A026257 36,69,70,71,39,40,75,76,41,77,42,82,83,84 %N A026257 a(n) = (1/2)*(s(n) + 1), where s(n) is the n-th odd number in A026255. %K A026257 nonn %O A026257 1,2 %A A026257 _Clark Kimberling_