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Search: id:A128435
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| A128435 |
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a(0)=a(1)=1. For n>=2, a(n) = number of positive integers which are <= n and are coprime to a(n-1)*a(n-2). |
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1
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| 1, 1, 2, 2, 2, 3, 2, 3, 3, 6, 3, 4, 4, 7, 6, 4, 5, 7, 13, 16, 9, 7, 13, 19, 22, 11, 12, 8, 9, 10, 8, 13, 15, 16, 9, 12, 12, 13, 12, 12, 13, 13, 39, 27, 28, 13, 18, 15, 13, 25, 37, 40, 20, 22, 20, 20, 22, 21, 14, 17, 24, 20, 17, 24, 20, 17, 24, 22, 21, 18, 20, 19, 27, 47, 49, 64, 33, 23
(list; graph; listen)
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OFFSET
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0,3
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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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a(7)*a(6) = 6. So a(8) is the number of positive integers which are <= 8 and are coprime to 6. There are 3 such integers (1,5,7), so a(8) = 3.
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MAPLE
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a[0]:=1: a[1]:=1: for n from 2 to 100 do ct:=0: for i from 1 to n do if igcd(i, a[n-1]*a[n-2])=1 then ct:=ct+1 else fi: od: a[n]:=ct: od: seq(a[n], n=0..100); - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 06 2007
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CROSSREFS
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Sequence in context: A137734 A078705 A050331 this_sequence A026903 A068324 A165015
Adjacent sequences: A128432 A128433 A128434 this_sequence A128436 A128437 A128438
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet May 05 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 06 2007
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