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Search: id:A067081
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| A067081 |
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Numbers n such that sigma(n+1)=2*sigma(n). |
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+0
5
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| 5, 125, 1253, 1673, 3127, 5191, 7615, 12035, 43817, 47795, 48559, 49955, 56975, 58373, 61721, 63545, 68033, 78395, 97411, 106001, 108473, 109939, 111451, 111683, 123497, 123797, 131659, 137081
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sequence seems to give odd values only.
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MATHEMATICA
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f[n_]:=DivisorSigma[1, n]; lst={}; Do[If[2*f[n]==f[n+1], AppendTo[lst, n]], {n, 9!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jul 22 2009]
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CROSSREFS
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Sequence in context: A012156 A071171 A113906 this_sequence A154022 A013710 A109345
Adjacent sequences: A067078 A067079 A067080 this_sequence A067082 A067083 A067084
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 18 2002
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