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Search: id:A127418
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| A127418 |
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a(1)=1; for n>1, a(n) = the number of earlier terms a(k), 1<k<=n-1, such that (a(k)+n) is coprime to k. |
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+0
2
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| 1, 1, 1, 3, 1, 5, 3, 6, 4, 7, 3, 10, 8, 8, 10, 11, 7, 11, 10, 13, 13, 14, 10, 18, 15, 16, 16, 17, 13, 20, 20, 16, 23, 21, 17, 25, 24, 21, 23, 25, 19, 30, 25, 25, 25, 29, 23, 36, 29, 29, 32, 33, 26, 41, 28, 37, 32, 37, 30, 41, 32, 41, 33, 42, 32, 51, 36, 44, 39, 43, 38, 52, 41, 44
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OFFSET
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1,4
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COMMENT
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The value of a(1) = 1 is arbitrary. a(1) can be any integer, and the rest of the sequence would remain unchanged.
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EXAMPLE
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a(1)+11 = 12 is coprime to 1; a(5)+11 = 12 is coprime to 5; and a(8)+11 = 17 is coprime to 8. These 3 are the only cases where (a(k)+11) is coprime to k, for 1 <=k <=10. So a(11) = 3.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[Table[GCD[l[[k]] + n, k], {k, n - 1}], 1]]]; Nest[f, {1}, 74] (*Chandler*)
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CROSSREFS
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Cf. A127417.
Sequence in context: A071168 A091926 A109606 this_sequence A099550 A099549 A078701
Adjacent sequences: A127415 A127416 A127417 this_sequence A127419 A127420 A127421
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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), Jan 13 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 22 2007
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