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Search: id:A125842
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| A125842 |
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a(1)=1. a(n) = the number of terms from among the first floor(n/2) terms of the sequence which are coprime to n. |
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2
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| 1, 1, 1, 2, 2, 3, 3, 3, 4, 3, 5, 3, 6, 5, 5, 6, 8, 3, 9, 7, 6, 8, 11, 4, 11, 9, 7, 10, 14, 3, 15, 11, 9, 11, 14, 6, 18, 13, 10, 11, 20, 6, 21, 14, 9, 15, 23, 8, 23, 13, 15, 17, 26, 10, 22, 16, 17, 18, 29, 7, 30, 20, 15, 21, 27, 8, 33, 23, 20, 17, 35, 12, 36, 23, 17, 24, 30, 12, 39, 21, 24
(list; graph; listen)
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OFFSET
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1,4
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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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The first floor(15/2) terms of the sequence are 1,1,1,2,2,3,3. Of these, five terms (1,1,1,2,2) are coprime to 15. So a(15) = 5.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l] + 1}, Append[l, Length[Select[Take[l, Floor[n/2]], GCD[ #, n] == 1 &]]]]; Nest[f, {1}, 80] (*Chandler*)
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CROSSREFS
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Cf. A125843.
Sequence in context: A000121 A049846 A086712 this_sequence A029865 A072644 A070082
Adjacent sequences: A125839 A125840 A125841 this_sequence A125843 A125844 A125845
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Dec 10 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 11 2006
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