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 A287419 #6 Jun 21 2022 15:31:54
%S A287419 1,6,8,12,14,16,21,22,26,30,32,34,39,40,44,46,51,53,57,59,61,64,69,71,
%T A287419 75,76,80,84,86,88,93,94,98,100,105,107,111,113,115,118,123,125,129,
%U A287419 130,134,136,141,143,147,149,151,156,157,161,165,167,169,174,175
%N A287419 Positions of 0 in A287418.
%C A287419 a(n) - a(n-1) is in {1,2,3,4,5} for n >= 1; also, 3n - a(n) is in {0, 1, 2} for n >= 1. The first 20 numbers 3n - a(n) are 2, 0, 1, 0, 1, 2, 0, 2, 1, 0, 1, 2, 0, 2, 1, 2, 0, 1, 0, 1, with 0 in positions given by A287420.
%H A287419 Clark Kimberling, <a href="/A287419/b287419.txt">Table of n, a(n) for n = 1..10000</a>
%t A287419 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 2, 0}, 2->{1, 0, 2}}] &, {0}, 9]; (*A287418*)
%t A287419 Flatten[Position[s, 0]]; (*A287419*)
%t A287419 Flatten[Position[s, 1]]; (*A287420*)
%t A287419 Flatten[Position[s, 2]]; (*A287421*)
%t A287419 Position[SubstitutionSystem[{0->{0,1,2},1->{1,2,0},2->{1,0,2}},{0},{5}][[1]],0]// Flatten (* _Harvey P. Dale_, Jun 21 2022 *)
%Y A287419 Cf. A287418, A287420, A287421.
%K A287419 nonn,easy
%O A287419 1,2
%A A287419 _Clark Kimberling_, May 25 2017