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 A287559 #4 May 31 2017 16:14:38
%S A287559 4,7,9,14,19,21,26,32,34,40,43,45,49,54,60,63,67,69,74,80,82,88,91,93,
%T A287559 97,102,108,111,116,119,121,126,129,134,140,143,148,151,153,158,163,
%U A287559 165,170,176,178,184,187,189,194,200,203,205,209,214,220,223,228
%N A287559 Positions of 2 in A287556.
%C A287559 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 0, 1, 3, 2, 1, 3, 2, 0, 2, 0, 1, 3, 3, 2, 0, 1, 1, 3, 2, 0, with
%C A287559 0 in positions given by A287557,
%C A287559 1 in positions given by A287558,
%C A287559 2 in positions given by A287560,
%C A287559 3 in positions given by A287559.
%H A287559 Clark Kimberling, <a href="/A287559/b287559.txt">Table of n, a(n) for n = 1..10000</a>
%t A287559 s = Nest[Flatten[# /. {0 -> {0, 1, 3, 2}, 1 -> {1, 3, 2, 0}, 2 -> {3, 2, 0, 1}, 3 -> {2, 0, 1, 3}}] &, {0}, 9]; (* A287556 *)
%t A287559 Flatten[Position[s, 0]]; (* A287557 *)
%t A287559 Flatten[Position[s, 1]]; (* A287558 *)
%t A287559 Flatten[Position[s, 2]]; (* A287559 *)
%t A287559 Flatten[Position[s, 3]]; (* A287560 *)
%Y A287559 Cf. A287556, A287557, A287558, A287560.
%K A287559 nonn,easy
%O A287559 1,1
%A A287559 _Clark Kimberling_, May 31 2017