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Search: id:A002659
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| A002659 |
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2*sigma(n) - 1.
(Formerly M3762 N1536)
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+0
3
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| 1, 5, 7, 13, 11, 23, 15, 29, 25, 35, 23, 55, 27, 47, 47, 61, 35, 77, 39, 83, 63, 71, 47, 119, 61, 83, 79, 111, 59, 143, 63, 125, 95, 107, 95, 181, 75, 119, 111, 179, 83, 191, 87, 167, 155, 143, 95, 247, 113, 185, 143, 195, 107, 239, 143, 239, 159, 179, 119, 335, 123, 191
(list; graph; listen)
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OFFSET
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1,2
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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).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
P. A. MacMahon, The connexion between the sum of the squares of the divisors and the number of partitions of a given number, Messenger Math., 54 (1924), 113-116.
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LINKS
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N. J. A. Sloane, Transforms
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FORMULA
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G.f. for Moebius transf.: (x + 2x^2 - x^3 ) / (1 - x )^2.
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PROGRAM
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(PARI) a(n)=if(n<1, 0, 2*sigma(n)-1)
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CROSSREFS
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Cf. A000203.
Sequence in context: A105054 A088897 A074755 this_sequence A164122 A166163 A050079
Adjacent sequences: A002656 A002657 A002658 this_sequence A002660 A002661 A002662
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KEYWORD
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easy,nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
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Better definition from Ralf Stephan, Nov 18 2004
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