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 A287458 #4 May 30 2017 12:15:44
%S A287458 3,4,7,10,15,16,19,22,27,28,31,36,39,40,43,46,51,52,55,58,63,64,69,70,
%T A287458 75,76,79,82,85,90,91,96,97,102,103,106,111,112,115,118,123,124,127,
%U A287458 130,135,136,139,144,147,148,151,154,159,160,163,166,171,172,177
%N A287458 Positions of 2 in A287455.
%C A287458 a(n) - a(n-1) is in {1, 3, 5} for n >= 1; also, 3n - a(n) is in {0, 1} for n >= 1. The first 20 numbers 3n - a(n) are 0, 2, 2, 2, 0, 2, 2, 2, 0, 2, 2, 0, 0, 2, 2, 2, 0, 2, 2, 2, with 0 in positions given by A287456.
%H A287458 Clark Kimberling, <a href="/A287458/b287458.txt">Table of n, a(n) for n = 1..10000</a>
%t A287458 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 0, 1}, 2->{2, 1, 0}}] &, {0}, 9]; (*A287455*)
%t A287458 Flatten[Position[s, 0]]; (*A287456*)
%t A287458 Flatten[Position[s, 1]]; (*A189666*)
%t A287458 Flatten[Position[s, 2]]; (*A287458*)
%Y A287458 Cf. A287455, A287456, A287458.
%K A287458 nonn,easy
%O A287458 1,1
%A A287458 _Clark Kimberling_, May 30 2017