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Search: id:A126261
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| A126261 |
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a(n) is the numerator of the sum of the reciprocals of the positive integers k, k<=n, where every positive integer <= k and coprime to k is also coprime to n. |
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+0
2
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| 1, 3, 11, 7, 137, 5, 363, 49, 19, 37, 83711, 7, 1145993, 167, 19, 1321, 42142223, 65, 275295799, 19, 43, 2887, 444316699, 133, 127, 1177, 18469, 85, 9227046511387, 23, 290774257297357, 3877999, 212, 22737, 971, 229, 2040798836801833, 233731, 1039
(list; graph; listen)
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OFFSET
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1,2
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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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The positive integers k, k <= 6, where every positive integer <=k and coprime to k is also coprime to 6, are 1,2,6. So a(6) = 5 is the numerator of 1 +1/2 +1/6 = 5/3.
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MATHEMATICA
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f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Plus @@ (1/# &) /@ Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &]; Table[Numerator[g[n]], {n, 40}] (*Chandler*)
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CROSSREFS
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Cf. A126260, A126262.
Sequence in context: A119324 A006495 A112286 this_sequence A050097 A070613 A084409
Adjacent sequences: A126258 A126259 A126260 this_sequence A126262 A126263 A126264
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KEYWORD
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frac,nonn
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AUTHOR
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Leroy Quet Dec 22 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 24 2006
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