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A058072
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Numbers n such that sigma(n) divides sigma(n+1), where sigma(n) is sum of positive divisors of n.
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2
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1, 5, 14, 125, 206, 957, 1253, 1334, 1364, 1634, 1673, 1919, 2685, 2759, 2974, 3127, 4364, 5191, 7615, 11219, 12035, 14841, 18873, 19358, 20145, 24957, 27089, 33998, 36566, 42818, 43817, 47795, 48559, 49955, 50039, 56564, 56975, 58373, 58463
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The ratio is always equal to 1, 2 or 3. A002961 is a subset of this sequence. - Paolo P. Lava (paoloplava(AT)gmail.com), Aug 23 2007
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EXAMPLE
| 5 is included because sigma(5) = 6 divides sigma(6) = 12.
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MAPLE
| with(numtheory); P:=proc(n) local a, i; for i from 1 by 1 to n do a:=sigma(i+1)/sigma(i); if trunc(a)=a then print(i); fi; od; end: P(100000); - Paolo P. Lava (paoloplava(AT)gmail.com), Aug 23 2007
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CROSSREFS
| Sequence in context: A024167 A077262 A184439 * A027304 A070135 A067857
Adjacent sequences: A058069 A058070 A058071 * A058073 A058074 A058075
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Nov 11 2000
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EXTENSIONS
| More terms from Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 27 2002
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