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 A287454 #4 May 30 2017 12:15:23
%S A287454 3,4,8,11,15,16,19,23,27,28,32,36,39,40,44,47,51,52,56,60,61,64,68,72,
%T A287454 75,76,80,83,87,88,91,95,99,102,103,107,111,112,116,119,123,124,127,
%U A287454 131,135,136,140,144,147,148,152,155,159,160,163,167,171,174,175
%N A287454 Positions of 2 in A287451.
%C A287454 a(n) - a(n-1) is in {1, 3, 4} for n >= 1; also, 3n - a(n) is in {0, 1, 2} for n >= 1. The first 20 numbers 3n - a(n) are 0, 2, 1, 1, 0, 2, 2, 1, 0, 2, 1, 0, 0, 2, 1, 1, 0, 2, 1, 0, with 0 in positions given by A287452, 1 in positions given by A287454, and 2 in positions given by A287453.
%H A287454 Clark Kimberling, <a href="/A287454/b287454.txt">Table of n, a(n) for n = 1..10000</a>
%t A287454 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 0, 1}, 2->{1, 2, 0}}] &, {0}, 9]; (*A287451*)
%t A287454 Flatten[Position[s, 0]]; (*A287452*)
%t A287454 Flatten[Position[s, 1]]; (*A287453*)
%t A287454 Flatten[Position[s, 2]]; (*A287454*)
%Y A287454 Cf. A287451, A287452, A287453.
%K A287454 nonn,easy
%O A287454 1,1
%A A287454 _Clark Kimberling_, May 30 2017