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Search: id:A060741
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| A060741 |
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Number of divisors of 2n which are also differences between consecutive divisors of 2n (ordered by size). |
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+0
7
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| 1, 2, 2, 3, 2, 3, 2, 4, 3, 4, 2, 4, 2, 4, 4, 5, 2, 5, 2, 4, 4, 4, 2, 5, 3, 4, 4, 4, 2, 7, 2, 6, 4, 4, 3, 6, 2, 4, 4, 5, 2, 5, 2, 6, 6, 4, 2, 6, 3, 6, 4, 6, 2, 7, 4, 4, 4, 4, 2, 9, 2, 4, 5, 7, 4, 5, 2, 6, 4, 6, 2, 8, 2, 4, 6, 6, 2, 6, 2, 6, 5, 4, 2, 8, 4, 4, 4, 6, 2, 9, 2, 6, 4, 4, 4, 7, 2, 6, 6, 6, 2, 6, 2, 6, 8
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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For odd numbers the intersection is empty.
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FORMULA
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a(n) = A000005(2n) - A060764(2n).
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EXAMPLE
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For n=35, 2n=70; divisors={1,2,5,7,10,14,35,70}; differences={1,3,2,3,4,21,35}; intersection={1,2,35}, so a(35)=3.
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MATHEMATICA
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a[n_ ] := Length[Intersection[Drop[d=Divisors[2n], 1]-Drop[d, -1], d]]
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CROSSREFS
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Cf. A060742, A060764.
Sequence in context: A135615 A166469 A080226 this_sequence A125747 A060129 A054030
Adjacent sequences: A060738 A060739 A060740 this_sequence A060742 A060743 A060744
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Apr 23 2001
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EXTENSIONS
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Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Jan 22 2002
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