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Search: id:A111291
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| 1, 4, 16, 92, 665, 5257, 44705, 394240, 3558181, 32608999, 302172507, 2823898245
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OFFSET
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0,2
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COMMENT
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Simon Colton conjectures that the number of refactorables less than x is at least x/(2 log(x)).
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LINKS
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S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.
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MATHEMATICA
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c = 0; k = 1; Do[ While[k <= 10^n, If[ Mod[k, DivisorSigma[0, k]] == 0, c++ ]; k++ ]; Print[c], {n, 0, 8}]
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CROSSREFS
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Cf. A033950.
Sequence in context: A139155 A003762 A143501 this_sequence A050913 A096243 A131928
Adjacent sequences: A111288 A111289 A111290 this_sequence A111292 A111293 A111294
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 01 2005
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EXTENSIONS
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a(9)-a(11) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 19 2009
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