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Search: id:A127433
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| A127433 |
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a(1)=1. a(n) = number of earlier terms a(k), 1<=k<=n-1, such that (k+n) is coprime to a(k). |
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+0
3
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| 1, 1, 2, 3, 2, 5, 4, 6, 4, 8, 5, 9, 7, 8, 8, 12, 9, 12, 9, 12, 13, 13, 14, 14, 14, 15, 17, 18, 13, 19, 18, 20, 21, 20, 22, 21, 22, 23, 20, 25, 22, 27, 23, 25, 26, 29, 29, 33, 27, 33, 29, 37, 32, 33, 33, 36, 33, 40, 34, 37, 37, 40, 37, 42, 38, 40, 41, 45, 37, 47, 42, 46, 45, 48, 46
(list; graph; listen)
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OFFSET
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1,3
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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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(1+9) is coprime to a(1)=1; (2+9) is coprime to a(2)=1; (4+9) is coprime to a(4)=3 and (8+9) is coprime to a(8)=6. These four cases are the only cases where (k+n) is coprime to a(k), for 1<=k<=8. So a(9) = 4.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[Table[GCD[k + n, l[[k]]], {k, n - 1}], 1]]]; Nest[f, {1}, 75] (*Chandler*)
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CROSSREFS
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Cf. A127431, A127434.
Sequence in context: A141658 A089587 A067316 this_sequence A055573 A072969 A139712
Adjacent sequences: A127430 A127431 A127432 this_sequence A127434 A127435 A127436
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jan 14 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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