A060663 Sigma(x) = n has exactly seven solutions.

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

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