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 A287554 #4 May 31 2017 15:46:56
%S A287554 3,6,9,16,18,21,28,31,33,40,43,46,52,55,58,61,66,69,76,79,81,88,91,94,
%T A287554 100,103,106,109,115,118,121,128,129,136,139,142,148,151,154,157,163,
%U A287554 166,169,176,178,181,188,191,196,199,202,205,211,214,217,224,226
%N A287554 Positions of 2 in A053839.
%C A287554 a(n) - a(n-1) is in {1,2,3,4,5,6,7} for n >= 1; also, 4n - a(n) is in {0,1,2,3} for n >= 1. The first 20 numbers 4n - a(n) are 1, 2, 3, 0, 2, 3, 0, 1, 3, 0, 1, 2, 0, 1, 2, 3, 2, 3, 0, 1, with
%C A287554 0 in positions given by A287555,
%C A287554 1 in positions given by A287552,
%C A287554 2 in positions given by A287553,
%C A287554 3 in positions given by A287554.
%H A287554 Clark Kimberling, <a href="/A287554/b287554.txt">Table of n, a(n) for n = 1..10000</a>
%t A287554 s = Nest[Flatten[# /. {0 -> {0, 1, 2, 3}, 1 -> {1, 2, 3, 0}, 2 -> {2, 3, 0, 1}, 3 -> {3, 0, 1, 2}}] &, {0}, 9]; (* A053839 *)
%t A287554 Flatten[Position[s, 0]]; (* A287552 *)
%t A287554 Flatten[Position[s, 1]]; (* A287553 *)
%t A287554 Flatten[Position[s, 2]]; (* A287554 *)
%t A287554 Flatten[Position[s, 3]]; (* A287555 *)
%Y A287554 Cf. A053839, A287552, A287553, A287555.
%K A287554 nonn,easy
%O A287554 1,1
%A A287554 _Clark Kimberling_, May 31 2017