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A023197
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Numbers k such that sigma(k) >= 3*k.
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15
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120, 180, 240, 360, 420, 480, 504, 540, 600, 660, 672, 720, 780, 840, 900, 960, 1008, 1080, 1200, 1260, 1320, 1344, 1440, 1512, 1560, 1584, 1620, 1680, 1800, 1848, 1872, 1890, 1920, 1980, 2016, 2040, 2100, 2160, 2184, 2280, 2340, 2352, 2376, 2400, 2520
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OFFSET
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1,1
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COMMENTS
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Sometimes called 3-abundant numbers (but compare the comments in A033880). The first odd number is A119240(3) = 1018976683725. - T. D. Noe, Mar 31 2011
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REFERENCES
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Melvyn B. Nathanson, Elementary Methods in Number Theory, Springer, 2000, p 260.
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..10000
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MAPLE
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select(t -> numtheory:-sigma(t) >= 3*t, [$1..10000]); # Robert Israel, Dec 28 2014
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MATHEMATICA
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Select[Range[10000], DivisorSigma[1, #] >= 3*#&] (* Vladimir Joseph Stephan Orlovsky, Apr 21 2010 *)
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CROSSREFS
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Cf. A119240. See A033880 for definition of k-abundancy.
Sequence in context: A189975 A232461 A090782 * A204828 A204830 A279088
Adjacent sequences: A023194 A023195 A023196 * A023198 A023199 A023200
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson
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STATUS
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approved
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