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Search: id:A060661
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| A060661 |
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Sigma(x) = n has exactly five solutions. |
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+0
1
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| 72, 144, 192, 216, 588, 600, 648, 792, 936, 992, 1056, 1224, 1302, 1320, 1560, 1736, 1980, 2040, 2088, 2112, 2268, 2448, 2730, 2790, 2912, 3038, 3136, 3312, 3472, 3520, 3534, 3552, 3672, 3792, 3816, 3936, 4056, 4092, 4340, 4440, 4864, 4872, 4920, 4960
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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72 = sigma(30) = sigma(46) = sigma(51) = sigma(55) = sigma(71).
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MATHEMATICA
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a = Table[ 0, {5000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 5001, a[ [ s ] ]++ ], {n, 1, 5000} ]; Select[ Range[ 5000 ], a[ [ # ] ] == 5 & ]
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CROSSREFS
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Cf. A007370, A007371, A007372.
Sequence in context: A090784 A143741 A157336 this_sequence A050495 A137883 A039498
Adjacent sequences: A060658 A060659 A060660 this_sequence A060662 A060663 A060664
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 18 2001
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