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Search: id:A117992
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| A117992 |
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Number of distinct rational numbers less than 1 that can be written as fractions of the first n composite numbers. |
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+0
2
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| 0, 1, 3, 5, 9, 11, 17, 20, 26, 29, 33, 38, 50, 54, 65, 80, 89, 98, 102, 113, 123, 144, 158, 166, 190, 203, 215, 222, 236, 247, 277, 287, 314, 328, 346, 364, 375, 400, 417, 438, 478, 487, 529, 548, 573, 604, 617, 641, 667, 683, 698, 749, 769, 796, 836, 851, 873
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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a(n) = (A117991(n) - 1)/2.
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EXAMPLE
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n=4, the first 4 composite numbers are 4,6, 8 and 9:
a(3)=#{4/6,4/8,4/9,6/8,6/9,8/9}=#{4/9,1/2,2/3,3/4,8/9}=5.
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CROSSREFS
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Cf. A015614.
Sequence in context: A076193 A056533 A114186 this_sequence A015614 A138203 A007952
Adjacent sequences: A117989 A117990 A117991 this_sequence A117993 A117994 A117995
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 08 2006
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