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A060661 Sigma(x) = n has exactly five solutions. 1
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; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

72 = sigma(30) = sigma(46) = sigma(51) = sigma(55) = sigma(71).

MATHEMATICA

a = Table[ 0, {5000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 5001, a[ [ s ] ]++ ], {n, 1, 5000} ]; Select[ Range[ 5000 ], a[ [ # ] ] == 5 & ]

With[{upto=5000}, Select[Union[Transpose[Select[Tally[DivisorSigma[ 1, Range[ upto]]], #[[2]]==5&]][[1]]], #<=upto&]] (* Harvey P. Dale, Jan 27 2015 *)

CROSSREFS

Cf. A007370, A007371, A007372.

Sequence in context: A227166 A250772 A157336 * A050495 A137883 A173728

Adjacent sequences:  A060658 A060659 A060660 * A060662 A060663 A060664

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 18 2001

STATUS

approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)