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Search: id:A064592
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| A064592 |
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Nonunitary doubly perfect numbers: the sum of the nonunitary divisors of n is 2n; i.e. sigma(n) - usigma(n) = 2n. |
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+0
6
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| 2520, 31320, 1163160, 2208384, 3053232, 6535296, 13472928, 123165600, 365959296, 4401782352, 5517818880, 612014161920
(list; graph; listen)
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OFFSET
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1,1
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MATHEMATICA
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nusigma[ n_ ] := DivisorSigma[ 1, n ]-Times@@(1+Power@@#&/@FactorInteger[ n ]); For[ n=1, True, n++, If[ nusigma[ n ]==2n, Print[ n ] ] ]
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CROSSREFS
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Cf. A048146, A064591, A064593, A064594, A064595, A064596.
Adjacent sequences: A064589 A064590 A064591 this_sequence A064593 A064594 A064595
Sequence in context: A068547 A094515 A066531 this_sequence A109480 A066599 A107531
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KEYWORD
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nonn,hard
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AUTHOR
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Dean Hickerson (dean(AT)math.ucdavis.edu), Sep 25, 2001
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EXTENSIONS
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There are no others up to 7.9*10^12, but here's a larger one: 2846972800010800140288
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