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 A287564 #4 May 31 2017 21:24:04
%S A287564 2,8,9,15,17,23,26,32,36,37,43,46,51,54,60,61,68,69,75,78,83,86,92,93,
%T A287564 98,104,105,111,113,119,122,128,129,135,138,144,148,149,155,158,163,
%U A287564 166,172,173,178,184,185,191,195,198,204,205,210,216,217,223,225
%N A287564 Positions of 2 in A287561.
%C A287564 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 2, 0, 3, 1, 3, 1, 2, 0, 0, 3, 1, 2, 1, 2, 0, 3, 0, 3, 1, 2, with
%C A287564 0 in positions given by A287564,
%C A287564 1 in positions given by A287565,
%C A287564 2 in positions given by A287562,
%C A287564 3 in positions given by A287563.
%H A287564 Clark Kimberling, <a href="/A287564/b287564.txt">Table of n, a(n) for n = 1..10000</a>
%t A287564 s = Nest[Flatten[# /. {0 -> {0, 2, 1, 3}, 1 -> {2, 1, 3, 0}, 2 -> {1, 3, 0, 2}, 3 -> {3, 0, 2, 1}}] &, {0}, 9]; (* A287561 *)
%t A287564 Flatten[Position[s, 0]]; (* A287562 *)
%t A287564 Flatten[Position[s, 1]]; (* A287563 *)
%t A287564 Flatten[Position[s, 2]]; (* A287564 *)
%t A287564 Flatten[Position[s, 3]]; (* A287565 *)
%Y A287564 Cf. A287561, A287562, A287563, A287565.
%K A287564 nonn,easy
%O A287564 1,1
%A A287564 _Clark Kimberling_, May 31 2017