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Search: id:A005276
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| A005276 |
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Betrothed (or quasi-amicable) numbers.
(Formerly M5291)
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+0
6
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| 48, 75, 140, 195, 1050, 1575, 1648, 1925, 2024, 2295, 5775, 6128, 8892, 9504, 16587, 20735, 62744, 75495, 186615, 196664, 199760, 206504, 219975, 266000, 309135, 312620
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Members of a pair (m,n) such that sigma(m)=sigma(n)=m+n+1, where sigma=A000203. [From M. F. Hasler (MHasler(AT)univ-ag.fr), Nov 04 2008]
Also members of a pair (m,k) such that m=sum of nontrivial divisors of k and k=sum of nontrivial divsors of m. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Sep 11 2009]
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. K. Guy, Unsolved Problems in Number Theory, B5.
P. Hagis and G. Lord, Quasi-amicable numbers, Math. Comp. 31 (1977), 608-611.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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FORMULA
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A005276 = A003502 union A003503. [From M. F. Hasler (MHasler(AT)univ-ag.fr), Nov 04 2008]
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PROGRAM
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Contribution from M. F. Hasler (MHasler(AT)univ-ag.fr), Nov 04 2008: (Start)
(PARI) isA005276(n) = { local(s=sigma(n)); s>n+1 & sigma(s-n-1)==s }
for( n=1, 10^6, isA005276(n) & print1(n", ")) (End)
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CROSSREFS
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Cf. A003502, A003503.
Sequence in context: A033821 A165039 A057533 this_sequence A143722 A110229 A108608
Adjacent sequences: A005273 A005274 A005275 this_sequence A005277 A005278 A005279
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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