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A086258
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a(n) is the smallest k such that 2^k+1 has n primitive prime factors.
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1
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0, 14, 26, 46, 83, 118, 309, 194, 414, 538, 786, 958
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OFFSET
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1,2
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COMMENTS
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A prime factor of 2^n+1 is called primitive if it does not divide 2^r+1 for any r<n. See A086257 for the number of primitive prime factors in 2^n+1. It is known that a(8) = 194.
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REFERENCES
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J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
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LINKS
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EXAMPLE
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a(2) = 14 because 2^14+1 = 5*29*113 and 29 and 113 do not divide 2^r+1 for r < 14.
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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