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 A287441 #4 May 29 2017 23:58:19
%S A287441 3,5,7,11,13,18,19,23,27,29,31,36,37,41,45,48,50,52,55,59,63,65,67,72,
%T A287441 75,77,79,83,85,90,91,95,99,102,104,106,109,113,117,119,121,126,129,
%U A287441 131,133,138,140,142,146,148,153,154,158,162,163,167,171,173,175
%N A287441 Positions of 2 in A287438.
%C A287441 a(n) - a(n-1) is in {1, 2, 3, 4, 5} for n >= 1; also, 3n - a(n) is in {0, 1, 2} for n >= 1.
%H A287441 Clark Kimberling, <a href="/A287441/b287441.txt">Table of n, a(n) for n = 1..10000</a>
%F A287441 a(n) + A287438(n) = 3n.
%t A287441 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 2, 0}, 2->{2, 1, 0}}] &, {0}, 9]; (*A287438*)
%t A287441 Flatten[Position[s, 0]]; (*A189728*)
%t A287441 Flatten[Position[s, 1]]; (*A189670*)
%t A287441 Flatten[Position[s, 2]]; (*A287441*)
%Y A287441 Cf. A287438, A189728, A189670.
%K A287441 nonn,easy
%O A287441 1,1
%A A287441 _Clark Kimberling_, May 26 2017