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Search: id:A067135
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| A067135 |
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Numbers n such that sigma(n+2)=2*sigma(n-2). |
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+0
2
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| 5, 13, 313, 1153, 26206, 100318, 111928, 160873, 363283, 644278, 1676428, 2097808, 2639518, 3875998, 5349238, 5738773, 5903638, 6045583, 11272903, 13192933, 17242333, 18234403, 19667998, 29520643, 29595193, 31944238, 36918448
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OFFSET
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1,1
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COMMENT
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For each term given here except 5, n+2 is divisible by 3, but that's not always true: n=149784995358 is a counterexample. Also, n+2 is divisible by 5 for all terms here except 5 and 26206, but it is also not true for n=70333261.
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MATHEMATICA
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Do[If[DivisorSigma[1, n+2] == 2*DivisorSigma[1, n-2], Print[n]], {n, 2, 10^9}] (Propper)
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CROSSREFS
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Cf. A067134.
Sequence in context: A124924 A124878 A085554 this_sequence A122900 A145557 A012033
Adjacent sequences: A067132 A067133 A067134 this_sequence A067136 A067137 A067138
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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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EXTENSIONS
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Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Feb 20 2002
More terms from Ryan Propper (rpropper(AT)stanford.edu), Sep 26 2005
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