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A068403
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Numbers n such that sigma(n)>3n.
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1
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180, 240, 360, 420, 480, 504, 540, 600, 660, 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, 2640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Davenport shows that these numbers have positive density. Are there good bounds for the density?
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REFERENCES
| Davenport, H. "Über numeri abundantes." Sitzungsber. Preuss. Akad. Wiss., Phys.-Math. Kl., No. 6 (1933), pp. 830-837.
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MATHEMATICA
| Select[Range[180, 7!, 2], 3*#<Plus@@Divisors[ # ]&] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 21 2010]
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CROSSREFS
| Terms not divisible by 6 are in A126104.
Sequence in context: A154360 A117551 A068545 * A030636 A179643 A160134
Adjacent sequences: A068400 A068401 A068402 * A068404 A068405 A068406
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 02 2002
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