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Search: id:A080907
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| A080907 |
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Numbers whose aliquot sequence terminates in a 1. |
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+0
10
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| 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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All primes are in this set because s(p) = 1 for p prime. Perfect numbers are clearly not in this set. Neither are aspiring numbers (A063769), or numbers whose aliquot sequence is a cycle (such as 220 and 284).
There are some numbers whose aliquot sequences haven't been fully determined (such as 276).
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FORMULA
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n is a member if n = 1 or s(n) is a member, where s(n) is the sum of the proper factors of n.
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EXAMPLE
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4 is in this set because its aliquot chain is 4->3->1. 6 is not in this set because it is perfect. 25 is not in this set because its aliquot chain is 25->6.
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CROSSREFS
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Cf. A063769, A115350.
Complement of A126016.
Sequence in context: A097010 A132999 A054027 this_sequence A127161 A129657 A103679
Adjacent sequences: A080904 A080905 A080906 this_sequence A080908 A080909 A080910
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KEYWORD
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nonn,nice
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AUTHOR
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Gabriel Cunningham (gcasey(AT)mit.edu), Mar 31 2003
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 14 2006
More terms from Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Dec 14 2006
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