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Search: id:A129456
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| A129456 |
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a(0)=1. a(n) = number of earlier terms of the sequence that are coprime to (n+a(n-1)). |
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2
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| 1, 1, 2, 3, 4, 4, 3, 4, 2, 9, 10, 8, 5, 3, 14, 15, 16, 12, 2, 12, 8, 21, 22, 13, 24, 23, 24, 17, 16, 17, 30, 31, 20, 33, 34, 22, 15, 15, 38, 34, 17, 18, 8, 23, 44, 45, 43, 10, 21, 15, 39, 10, 23, 25, 54, 55, 36, 35, 36, 44, 26, 39, 62, 49, 64, 41, 66, 61, 43, 29, 41, 31, 72, 58, 21
(list; graph; listen)
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OFFSET
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0,3
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EXAMPLE
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11 + a(10) = 21. There are 8 terms among a(0),a(1),..,a(10) that are coprime to 21. (These terms are a(0),a(1),a(2),a(4),a(5),a(7),a(8),and a(10).) So a(11) = 8.
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MAPLE
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a[0]:=1: for n from 1 to 120 do ct:=0: for i from 0 to n-1 do if igcd(a[i], n+a[n-1])=1 then ct:=ct+1 else ct:=ct: fi: od: a[n]:=ct: od: seq(a[n], n=0..100); - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2007
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CROSSREFS
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Cf. A129457.
Sequence in context: A107898 A128863 A117391 this_sequence A030412 A059686 A101083
Adjacent sequences: A129453 A129454 A129455 this_sequence A129457 A129458 A129459
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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), Apr 16 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2007
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