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A064591
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Nonunitary perfect numbers: n is the sum of its nonunitary divisors; i.e. sigma(n) - usigma(n) = n.
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9
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OFFSET
| 1,1
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COMMENTS
| If P is an even perfect number, then 4P is in the sequence. Are there any others?
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EXAMPLE
| The sum of the nonunitary divisors of 24 is 2+4+6+12 = 24.
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MATHEMATICA
| nusigma[ n_ ] := DivisorSigma[ 1, n ]-Times@@(1+Power@@#&/@FactorInteger[ n ]); For[ n=1, True, n++, If[ nusigma[ n ]==n, Print[ n ] ] ]
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CROSSREFS
| Cf. A048146, A064592, A064593, A064594, A064595, A064596, A064597, A064598, A064599, A063870.
Sequence in context: A103473 A162451 A064595 * A124952 A126411 A137799
Adjacent sequences: A064588 A064589 A064590 * A064592 A064593 A064594
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KEYWORD
| nonn,hard
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AUTHOR
| Dean Hickerson (dean.hickerson(AT)yahoo.com), Sep 25, 2001
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EXTENSIONS
| There are no others up to 1.2*10^14.
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