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%I #4 May 31 2017 21:24:12
%S 4,6,11,13,19,21,28,30,34,39,41,48,49,56,58,63,66,71,73,80,81,88,90,
%T 95,100,102,107,109,115,117,124,126,131,133,140,142,146,151,153,160,
%U 161,168,170,175,180,182,187,189,193,200,202,207,212,214,219,221,227
%N Positions of 3 in A287561.
%C 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, 2, 1, 3, 1, 3, 0, 2, 2, 1, 3, 0, 3, 0, 2, 1, 2, 1, 3, 0, with
%C 0 in positions given by A287562,
%C 1 in positions given by A287563,
%C 2 in positions given by A287564,
%C 3 in positions given by A287565.
%H Clark Kimberling, <a href="/A287565/b287565.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = 4n - A287561(n) for n >= 1.
%t 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 Flatten[Position[s, 0]]; (* A287562 *)
%t Flatten[Position[s, 1]]; (* A287563 *)
%t Flatten[Position[s, 2]]; (* A287564 *)
%t Flatten[Position[s, 3]]; (* A287565 *)
%Y Cf. A287561, A287562, A287563, A287565.
%K nonn,easy
%O 1,1
%A _Clark Kimberling_, May 31 2017
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