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 A159917 #13 Aug 16 2016 12:11:56
%S A159917 0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,2,0,1,
%T A159917 0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,2,0,1,
%U A159917 0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2,0,1,0,1,2,0,1,2,0,1,0,1,2
%N A159917 Fixed point of the morphism 0 -> 01, 1 -> 2, 2 -> 01, starting from a(0) = 0.
%C A159917 Equals A003714 mod 4.
%H A159917 F. Michel Dekking, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL19/Dekking/dekk4.html">Morphisms, Symbolic Sequences, and Their Standard Forms</a>, Journal of Integer Sequences, Vol. 19 (2016), Article 16.1.1.
%t A159917 Nest[Flatten[ # /. {0 -> {0, 1}, 1 -> {2}, 2 -> {0, 1}}] &, {0}, 10] (* _Robert G. Wilson v_, Apr 27 2009 *)
%K A159917 nonn
%O A159917 0,3
%A A159917 _Philippe Deléham_, Apr 25 2009
%E A159917 Name changed by _Robert G. Wilson v_, Apr 27 2009
%E A159917 More terms from _Robert G. Wilson v_, Apr 27 2009