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A060660 Sigma(x) = n has exactly four solutions. 0
96, 120, 180, 312, 372, 420, 434, 456, 540, 546, 560, 624, 702, 728, 798, 816, 930, 1064, 1120, 1170, 1404, 1632, 1638, 1674, 1710, 1776, 1792, 1944, 2100, 2240, 2544, 2560, 2664, 2760, 2800, 2844, 2856, 2940, 2952, 3000, 3040, 3048, 3060, 3080, 3096 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

96 = sigma(42) = sigma(62) = sigma(69) = sigma(77).

MATHEMATICA

a = Table[ 0, {5000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 5001, a[ [ s ] ]++ ], {n, 1, 5000} ]; Select[ Range[ 5000 ], a[ [ # ] ] == 4 & ]

CROSSREFS

Cf. A007370, A007371, A007372.

Sequence in context: A257411 A175116 A153484 * A258748 A323629 A146992

Adjacent sequences:  A060657 A060658 A060659 * A060661 A060662 A060663

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Apr 18 2001

STATUS

approved

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Last modified December 6 08:53 EST 2019. Contains 329788 sequences. (Running on oeis4.)