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%I #4 May 25 2017 17:53:53
%S 3,4,9,12,13,18,19,24,27,28,33,36,39,40,45,48,49,54,57,58,63,66,67,72,
%T 73,78,81,84,85,90,93,94,99,100,105,108,109,114,117,120,121,126,129,
%U 130,135,138,139,144,147,148,153,154,159,162,163,168,171,174,175
%N Positions of 2 in A287397.
%C a(n) - a(n-1) is in {1,3,5} for n >= 1; also, 3n - a(n) is in {0, 2} for n >= 1. The first 20 numbers 3n - a(n) are 0, 2, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 0, 2, 0, 0, 2, 0, 0, 2, with 2 in positions given by A287399.
%H Clark Kimberling, <a href="/A287400/b287400.txt">Table of n, a(n) for n = 1..10000</a>
%t s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 1, 0}, 2->{1, 0, 2}}] &, {0}, 9]; (*A287397*)
%t Flatten[Position[s, 0]]; (*A287398*)
%t Flatten[Position[s, 1]]; (*A287399*)
%t Flatten[Position[s, 2]]; (*A287400*)
%Y Cf. A287397, A287398, A287399.
%K nonn,easy
%O 1,1
%A _Clark Kimberling_, May 25 2017
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