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Search: id:A058073
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| A058073 |
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Numbers n such that sigma(n+1) divides sigma(n), where sigma(n) is sum of positive divisors of n. |
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+0
4
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| 12, 14, 70, 88, 180, 204, 206, 220, 957, 1334, 1364, 1634, 1750, 1888, 2685, 2958, 2974, 4364, 8142, 8632, 9114, 12000, 14664, 14841, 18414, 18762, 18873, 19358, 20118, 20145, 20712, 24957, 25194, 30996, 33998, 36566, 42818, 45520, 47940
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The ratio is always equal to 1, 2 or 3. A002961 is a subset of this sequence. - Paolo P. Lava (ppl(AT)spl.at), Aug 23 2007
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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12 is included because sigma(13) = 14 divides sigma(12) = 28.
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MATHEMATICA
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Select[Range[50000], Mod[DivisorSigma[1, # ], DivisorSigma[1, # + 1]] == 0 &]
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CROSSREFS
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Sequence in context: A022326 A127401 A106135 this_sequence A058951 A002926 A139310
Adjacent sequences: A058070 A058071 A058072 this_sequence A058074 A058075 A058076
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Nov 11 2000
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EXTENSIONS
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More terms from Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 27 2002
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