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A060663 Sigma(x) = n has exactly seven solutions. 1
240, 684, 744, 912, 1092, 1176, 1200, 1368, 1596, 2340, 2376, 2496, 2700, 3072, 3348, 4212, 5460, 5520, 5586, 5642, 5712, 6000, 6160, 6264, 6804, 6864, 7068, 7254, 7584, 7632, 7728, 8112, 8232, 8370, 8512, 8680, 8712, 8832, 8960, 9744, 9936 (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

240 = sigma(114) = sigma(135) = sigma(158) = sigma(177) = sigma(203) = sigma(209) = sigma(239).

MATHEMATICA

a = Table[ 0, {10000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 10001, a[ [ s ] ]++ ], {n, 1, 10000} ]; Select[ Range[ 10000 ], a[ [ # ] ] == 7 & ]

With[{upto=10000}, Select[Tally[DivisorSigma[1, Range[upto]]], #[[2]]==7 && #[[1]] <= upto&]][[All, 1]]//Sort (* Harvey P. Dale, Jun 22 2019 *)

CROSSREFS

Cf. A007370, A007371, A007372.

Sequence in context: A263161 A268772 A202196 * A092000 A124352 A158562

Adjacent sequences:  A060660 A060661 A060662 * A060664 A060665 A060666

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 18 2001

STATUS

approved

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Last modified October 17 12:14 EDT 2019. Contains 328111 sequences. (Running on oeis4.)