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Search: id:A086258
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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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+0
2
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OFFSET
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1,2
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COMMENT
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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.
Next term is > 666. - David Wasserman (wasserma(AT)spawar.navy.mil), Feb 25 2005
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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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J. Brillhart et al., Factorizations of b^n +- 1 Available on-line
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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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Cf. A086257.
Cf. A086252.
Sequence in context: A079702 A082773 A112772 this_sequence A063799 A086451 A040182
Adjacent sequences: A086255 A086256 A086257 this_sequence A086259 A086260 A086261
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KEYWORD
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hard,more,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Jul 14 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 25 2005
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