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Search: id:A097559
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| A097559 |
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a(n) = number of terms among {a(1),a(2),a(3),...a(n-1)} which are coprime to n; a(1)=2. |
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+0
2
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| 2, 0, 1, 1, 3, 2, 5, 4, 6, 3, 9, 3, 11, 8, 7, 9, 15, 5, 17, 10, 11, 12, 21, 8, 19, 16, 16, 14, 27, 7, 29, 19, 19, 20, 24, 13, 35, 20, 25, 19, 39, 14, 41, 25, 23, 28, 45, 20, 40, 23, 35, 30, 51, 22, 36, 28, 35, 33, 57, 16, 59, 37, 34, 38, 46, 23, 65, 38, 45, 27, 69, 27, 71, 44, 38, 40
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A family of related sequences can be generated using different positive integers for a(1). (a(1)=1 is sequence A096216.)
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EXAMPLE
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a(8)=4 because among the first seven terms, namely 2,0,1,1,3,2,5, there are 4 terms that are relatively prime to 8 (1,1,3,and 5).
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MAPLE
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a[1]:=2: for n from 2 to 100 do s:=0: for j from 1 to n-1 do if gcd(a[j], n)=1 then s:=s+1 else s:=s fi od: a[n]:=s: od: seq(a[n], n=1..84); (Deutsch)
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MATHEMATICA
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a[1] = 2; a[n_] := a[n] = Count[ GCD[ Table[ a[i], {i, n - 1}], n], 1]; Array[a, 76] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 27 2005)
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CROSSREFS
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Cf. A096216.
Sequence in context: A068446 A107261 A035788 this_sequence A123226 A102210 A124220
Adjacent sequences: A097556 A097557 A097558 this_sequence A097560 A097561 A097562
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Aug 27 2004
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 03 2005
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