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A129291
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a(n) = 1 - 3^(3^n) + 9^(3^n).
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1
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OFFSET
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0,1
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COMMENTS
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a(n) is the ratio of two consecutive base-3 Fermat numbers A129290(n) = 3^(3^n) + 1 = {4, 28, 19684, 7625597484988, ...}.
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LINKS
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FORMULA
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MATHEMATICA
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Table[1 - 3^3^n + 9^3^n, {n, 0, 5}]
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CROSSREFS
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Cf. A002061 (central polygonal numbers: n^2 - n + 1).
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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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