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Search: id:A087080
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| A087080 |
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Number of elements in the coprime subsets of the integers 1 to n. |
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+0
4
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| 0, 1, 4, 12, 20, 52, 60, 148, 196, 300, 332, 780, 828, 1904, 2080, 2348, 2812, 6352, 6608, 14736, 15632, 17456, 18640, 41152, 42432, 60912, 64800, 80928, 85408, 186304, 187584, 406400, 457344, 497472, 523456, 585280, 596288, 1284224
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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A coprime set of integers has (m,n)=1 for each pair of integers in the set.
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REFERENCES
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Alan Sutcliffe, Divisors and Common Factors in Sets of Integers, awaiting publication.
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EXAMPLE
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a(4)=12 since the 12 coprime subsets of (1,2,3,4) are ( ) (1) (2) (3) (4) (1,2) (1,3) (1,4) (2,3) (3,4) (1,2,3) (1,3 4) and these contain 20 elements.
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CROSSREFS
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A087077 gives the number of elements in the primitive subsets. A084422 gives the number coprime subsets. A087081 gives the sum of the elements in coprime subsets.
Sequence in context: A099956 A008092 A151914 this_sequence A134253 A115106 A047965
Adjacent sequences: A087077 A087078 A087079 this_sequence A087081 A087082 A087083
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KEYWORD
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nonn
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AUTHOR
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Alan Sutcliffe (alansut(AT)ntlworld.com), Aug 12 2003
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