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 A120126 #2 Mar 31 2012 13:21:31 %S A120126 0,1,2,3,4,5,6,7,8,9,10,5654,15,20,35,45,50,55,39,29,21,64,5064,11,25, %T A120126 30,40,46,56,34,16,73,51,890,31,26,36,41,60,44,42,82,61,57,285,12,17, %U A120126 22,47,52,37,106,69,65,74,258,23,18,43,62,27,113,75,70,66,58,157,13,32,48 %N A120126 Index of first occurrence of n in A120125, or 0 if not present. %C A120126 a(0) = 0 is an index, not the default. 111 is the smallest number that does not occur in A120125. %Y A120126 Cf. A120125. %K A120126 base,nonn %O A120126 0,3 %A A120126 _Franklin T. Adams-Watters_, Jun 09 2006