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 A287443 #8 Jun 01 2017 10:15:56
%S A287443 0,1,2,2,0,1,0,2,1,0,2,1,0,1,2,2,0,1,0,1,2,0,2,1,2,0,1,0,1,2,0,2,1,2,
%T A287443 0,1,0,1,2,2,0,1,0,2,1,0,2,1,0,1,2,2,0,1,0,1,2,2,0,1,0,2,1,0,1,2,0,2,
%U A287443 1,2,0,1,0,2,1,0,1,2,2,0,1,0,1,2,2,0
%N A287443 Start with 0 and repeatedly substitute 0->012, 1->201, 2->021.
%C A287443 This is the fixed point of the morphism 0->012, 1->201, 2->021 starting with 0. Let u be the (nonperiodic) sequence of positions of 0, and likewise, v for 1 and w for 2; then u(n)/n -> 3, v(n)/n -> 3, w(n)/n -> 3.
%C A287443 See A287385 for a guide to related sequences.
%H A287443 Clark Kimberling, <a href="/A287443/b287443.txt">Table of n, a(n) for n = 1..10000</a>
%H A287443 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%e A287443 First three iterations of the morphism: 012, 012201021, 012201021021012201012021201.
%t A287443 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 0, 1}, 2->{0, 2, 1}}] &, {0}, 9]; (*A287443*)
%t A287443 Flatten[Position[s, 0]]; (*A287444*)
%t A287443 Flatten[Position[s, 1]]; (*A287445*)
%t A287443 Flatten[Position[s, 2]]; (*A287446*)
%Y A287443 Cf. A287385, A287444, A287445, A287446.
%K A287443 nonn,easy
%O A287443 1,3
%A A287443 _Clark Kimberling_, May 26 2017