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Search: id:A134639
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| A134639 |
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Conjectured number of numbers k such that sigma(k)/k = n. |
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+0
2
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OFFSET
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3,1
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COMMENT
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These numbers come from Guy and Flammenkamp. Sequences A000396, A005820, A027687, A046060, and A046061 give the k for which the abundancy sigma(k)/k is 2, 3, 4, 5, and 6, respectively. Sequence A054030 gives the abundancy of each multiperfect number A007691.
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, 3rd Ed., New York, Springer-Verlag, 2004, Section B2.
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LINKS
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Achim Flammenkamp, The Multiply Perfect Numbers Page
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CROSSREFS
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Sequence in context: A047792 A121026 A036148 this_sequence A069497 A139249 A141277
Adjacent sequences: A134636 A134637 A134638 this_sequence A134640 A134641 A134642
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Nov 05 2007
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