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 A287516 #10 Dec 22 2024 10:24:07
%S A287516 0,1,2,1,0,2,0,2,1,1,0,2,0,1,2,0,2,1,0,1,2,0,2,1,1,0,2,1,0,2,0,1,2,0,
%T A287516 2,1,0,1,2,1,0,2,0,2,1,0,1,2,0,2,1,1,0,2,0,1,2,1,0,2,0,2,1,0,1,2,0,2,
%U A287516 1,1,0,2,1,0,2,0,1,2,0,2,1,1,0,2,0,1
%N A287516 Start with 0 and repeatedly substitute 0->012, 1->102, 2->021.
%C A287516 This is the fixed point of the morphism 0->012, 1->102, 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 A287516 See A287385 for a guide to related sequences.
%H A287516 Clark Kimberling, <a href="/A287516/b287516.txt">Table of n, a(n) for n = 1..10000</a>
%H A287516 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%e A287516 First three iterations of the morphism: 012, 012102021, 012102021102012021012021102.
%t A287516 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 0, 2}, 2->{0, 2, 1}}] &, {0}, 9]; (*A287516*)
%t A287516 Flatten[Position[s, 0]]; (*A287517*)
%t A287516 Flatten[Position[s, 1]]; (*A287518*)
%t A287516 Flatten[Position[s, 2]]; (*A287519*)
%t A287516 SubstitutionSystem[{0->{0,1,2},1->{1,0,2},2->{0,2,1}},{0},{5}][[1]] (* _Harvey P. Dale_, Dec 22 2024 *)
%Y A287516 Cf. A287385, A287517, A287518, A287519.
%K A287516 nonn,easy
%O A287516 1,3
%A A287516 _Clark Kimberling_, May 30 2017