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Search: id:A064599
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| A064599 |
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The sum of the nonunitary divisors of n is a divisor of n; i.e. sigma(n) - usigma(n) divides n. |
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+0
2
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| 4, 9, 18, 24, 25, 49, 112, 121, 169, 289, 361, 529, 841, 961, 1369, 1681, 1849, 1984, 2209, 2809, 3481, 3721, 4489, 5041, 5329, 6241, 6889, 7921, 9409, 10201, 10609, 11449, 11881, 12769, 16129, 17161, 18769, 19321, 22201, 22801, 24649, 26569
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The sequence consists of the nonunitary perfect numbers (A064591), squares of primes (A001248), and 18.
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MATHEMATICA
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nusigma[ n_ ] := DivisorSigma[ 1, n ]-Times@@(1+Power@@#&/@FactorInteger[ n ]); For[ n=1, True, n++, v=nusigma[ n ]; If[ v>0&&Mod[ n, v ]==0, Print[ n ] ] ]
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CROSSREFS
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Cf. A048146, A064591.
Adjacent sequences: A064596 A064597 A064598 this_sequence A064600 A064601 A064602
Sequence in context: A008236 A088365 A139468 this_sequence A062952 A100435 A026412
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KEYWORD
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nonn,easy
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AUTHOR
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Dean Hickerson (dean(AT)math.ucdavis.edu), Sep 25, 2001
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