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A127726
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Numbers n that are 3-imperfect.
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2
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6, 120, 126, 2520, 2640, 30240, 32640, 37800, 37926, 55440, 685440, 758520, 831600, 2600640, 5533920, 6917400, 9102240, 10281600, 11377800, 16687440, 152182800, 206317440, 250311600, 475917120, 866829600, 1665709920, 1881532800
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The new terms come from the paper by Zhou and Zhu. This sequence also contains n = 9223372034707292160 = 2^31*3*5*17*257*65537, which has the product of five Fermat primes (A019434). For this n, n/3 is a 2-imperfect number (A127725). [From T. D. Noe (noe(AT)sspectra.com), Apr 03 2009]
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REFERENCES
| L. Toth, A survey of the alternating sum-of-divisors function, arXiv:1111.4842, 2011
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LINKS
| Weiyi Zhou and Long Zhu, On k-imperfect numbers, INTEGERS: Electronic Journal of Combinatorial Number Theory, 9 (2009), #A01. [From T. D. Noe (noe(AT)sspectra.com), Apr 03 2009]
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CROSSREFS
| Cf. A127724 (k-imperfect numbers).
Sequence in context: A135869 A054957 A081537 * A117063 A178911 A001219
Adjacent sequences: A127723 A127724 A127725 * A127727 A127728 A127729
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KEYWORD
| nonn,changed
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Jan 25 2007
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EXTENSIONS
| Extended by T. D. Noe (noe(AT)sspectra.com), Apr 03 2009
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