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 A287452 #4 May 30 2017 12:15:10
%S A287452 1,5,9,12,13,17,20,24,25,29,33,34,37,41,45,48,49,53,57,58,62,65,69,70,
%T A287452 73,77,81,84,85,89,92,96,97,100,104,108,109,113,117,120,121,125,128,
%U A287452 132,133,137,141,142,145,149,153,156,157,161,164,168,169,172,176
%N A287452 Positions of 0 in A287451.
%C A287452 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 2, 1, 0, 0, 2, 1, 1, 0, 2, 1, 0, 2, 2, 1, 0, 0, 2, 1, 0, 2, with 0 in positions given by A287454, 1 in positions given by A287453, and 2 in positions given by A287452.
%H A287452 Clark Kimberling, <a href="/A287452/b287452.txt">Table of n, a(n) for n = 1..10000</a>
%t A287452 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 0, 1}, 2->{1, 2, 0}}] &, {0}, 9]; (*A287451*)
%t A287452 Flatten[Position[s, 0]]; (*A287452*)
%t A287452 Flatten[Position[s, 1]]; (*A287453*)
%t A287452 Flatten[Position[s, 2]]; (*A287454*)
%Y A287452 Cf. A287451, A287453, A287454.
%K A287452 nonn,easy
%O A287452 1,2
%A A287452 _Clark Kimberling_, May 30 2017