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A224512
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Gray code variant of A147582.
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2
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1, 4, 12, 4, 12, 36, 12, 4, 12, 36, 108, 36, 12, 36, 12, 4, 12, 36, 108, 36, 108, 324, 108, 36, 12, 36, 108, 36, 12, 36, 12, 4, 12, 36, 108, 36, 108, 324, 108, 36, 108, 324, 972, 324, 108, 324, 108, 36, 12, 36, 108, 36, 108, 324, 108, 36, 12, 36, 108
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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a(1) = 1. For a(n)>1, a(n) = 4 * 3^(gt(n-1)-1).
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EXAMPLE
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A003188(5-1) = 6 = 110 (base 2), so gt(5-1) = 2. Then a(5) = 12 = 4 * 3^1 = 12.
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PROG
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(PARI) gt(n) = sum(kk=1, n, (-1)^((kk/2^valuation(kk, 2)-1)/2)); \\ from A005811.
a(n) = if (n==1, 1, 4 * 3^(gt(n-1)-1)); \\ Michel Marcus, Apr 22 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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