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 A026338 #4 Mar 30 2012 18:56:06 %S A026338 1,1,2,3,2,4,3,5,6,4,7,8,5,6,9,10,7,11,8,12,13,14,9,15,10,16,17,11,18, %T A026338 19,12,13,20,14,21,22,15,23,24,16,17,25,26,18,27,19,28,29,30,20,31,32, %U A026338 21,33,22,34,35,23,24,36,37,38,39,25,26,40 %N A026338 a(n) = a(m) if a(m) has already occurred exactly once and n = m+[ m/2 ]+1, else a(n) = least positive integer that has not yet occurred. %K A026338 nonn %O A026338 1,3 %A A026338 _Clark Kimberling_