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 A287323 #4 May 23 2017 14:32:46
%S A287323 3,4,9,10,13,14,17,18,27,28,33,34,39,40,43,44,47,48,57,58,61,62,65,66,
%T A287323 75,76,79,80,83,84,93,94,103,104,113,114,119,120,125,126,129,130,133,
%U A287323 134,143,144,149,150,155,156,159,160,163,164,173,174,179,180,185
%N A287323 Positions of 2 in A287320.
%H A287323 Clark Kimberling, <a href="/A287323/b287323.txt">Table of n, a(n) for n = 1..10000</a>
%t A287323 s = Nest[Flatten[# /. {0 -> {1, 0}, 1 -> {2, 2}, 2 -> 0}] &, {0}, 9] (* A287175 *)
%t A287323 Flatten[Position[s, 0]] (* A287321 *)
%t A287323 Flatten[Position[s, 1]] (* A287322 *)
%t A287323 Flatten[Position[s, 2]] (* A287323 *)
%Y A287323 Cf. A287320, A287321, A287322.
%K A287323 nonn,easy
%O A287323 1,1
%A A287323 _Clark Kimberling_, May 23 2017