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 A287418 #10 Oct 09 2023 13:38:14
%S A287418 0,1,2,1,2,0,1,0,2,1,2,0,1,0,2,0,1,2,1,2,0,0,1,2,1,0,2,1,2,0,1,0,2,0,
%T A287418 1,2,1,2,0,0,1,2,1,0,2,0,1,2,1,2,0,1,0,2,1,2,0,1,0,2,0,1,2,0,1,2,1,2,
%U A287418 0,1,0,2,1,2,0,0,1,2,1,0,2,1,2,0,1,0
%N A287418 Start with 0 and repeatedly substitute 0->012, 1->120, 2->102.
%C A287418 This is the fixed point of the morphism 0->012, 1->120, 2->102 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 A287418 See A287385 for a guide to related sequences.
%H A287418 Clark Kimberling, <a href="/A287418/b287418.txt">Table of n, a(n) for n = 1..10000</a>
%H A287418 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%e A287418 First three iterations of the morphism: 012, 012120102, 012120102120102012120012102.
%t A287418 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 2, 0}, 2->{1, 0, 2}}] &, {0}, 9]; (*A287418*)
%t A287418 Flatten[Position[s, 0]]; (*A287419*)
%t A287418 Flatten[Position[s, 1]]; (*A287420*)
%t A287418 Flatten[Position[s, 2]]; (*A287421*)
%t A287418 SubstitutionSystem[{0->{0,1,2},1->{1,2,0},2->{1,0,2}},{0},{5}][[1]] (* _Harvey P. Dale_, Oct 09 2023 *)
%Y A287418 Cf. A287385, A287419, A287420, A287421.
%K A287418 nonn,easy
%O A287418 1,3
%A A287418 _Clark Kimberling_, May 25 2017