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 A081592 #5 Mar 30 2012 18:39:16 %S A081592 1,2,1,2,2,1,1,1,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, %T A081592 1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, %U A081592 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2 %N A081592 A self generating sequence: "there are n a(n)'s in the sequence". Start with 1,2 and use the rule : "a(n)=k implies there are n following k's (k is 1 or 2)". %C A081592 Lengths of runs of consecutive 1's or 2's are : 1,1,2,3,9,21,117,588 ... %e A081592 Sequence begins : 1,2 . Since a(1)=1 there is only one following "1", gives 1,2,1. Since a(2)=2 there are 2 following "2's", gives 1,2,1,2,2. Since a(3)=1 there are 3 following "1's" 1,2,1,2,2,1,1,1 etc. %K A081592 nonn %O A081592 1,2 %A A081592 _Benoit Cloitre_, Apr 21 2003