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A127725
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Numbers n that are 2-imperfect.
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3
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OFFSET
| 1,1
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COMMENTS
| This sequence also contains n = 3074457344902430720 = 2^31*5*17*257*65537, which has the product of four Fermat primes (A019434). For this n, 3*n is a 3-imperfect number (A127726). [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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CROSSREFS
| Cf. A127724 (k-imperfect numbers).
Sequence in context: A110953 A003683 A098519 * A185619 A048014 A094702
Adjacent sequences: A127722 A127723 A127724 * A127726 A127727 A127728
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KEYWORD
| nonn,more,changed
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Jan 25 2007
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