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`%I #4 May 31 2017 15:46:56
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`%S 3,6,9,16,18,21,28,31,33,40,43,46,52,55,58,61,66,69,76,79,81,88,91,94,
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`%T 100,103,106,109,115,118,121,128,129,136,139,142,148,151,154,157,163,
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`%U 166,169,176,178,181,188,191,196,199,202,205,211,214,217,224,226
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`%N Positions of 2 in A053839.
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`%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 1, 2, 3, 0, 2, 3, 0, 1, 3, 0, 1, 2, 0, 1, 2, 3, 2, 3, 0, 1, with
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`%C 0 in positions given by A287555,
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`%C 1 in positions given by A287552,
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`%C 2 in positions given by A287553,
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`%C 3 in positions given by A287554.
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`%H Clark Kimberling, <a href="/A287554/b287554.txt">Table of n, a(n) for n = 1..10000</a>
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`%t s = Nest[Flatten[# /. {0 -> {0, 1, 2, 3}, 1 -> {1, 2, 3, 0}, 2 -> {2, 3, 0, 1}, 3 -> {3, 0, 1, 2}}] &, {0}, 9]; (* A053839 *)
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`%t Flatten[Position[s, 0]]; (* A287552 *)
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`%t Flatten[Position[s, 1]]; (* A287553 *)
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`%t Flatten[Position[s, 2]]; (* A287554 *)
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`%t Flatten[Position[s, 3]]; (* A287555 *)
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`%Y Cf. A053839, A287552, A287553, A287555.
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`%K nonn,easy
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`%O 1,1
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`%A _Clark Kimberling_, May 31 2017
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