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Search: id:A126262
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| A126262 |
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a(n) is the denominator 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, 2, 6, 4, 60, 3, 140, 24, 9, 20, 27720, 4, 360360, 84, 10, 560, 12252240, 36, 77597520, 10, 21, 1320, 118982864, 72, 50, 520, 7560, 42, 2329089562800, 15, 72201776446800, 1441440, 99, 9520, 420, 120, 485721041551200, 95760, 468, 24, 19914562703599200
(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) = 3 is the denominator 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[Denominator[g[n]], {n, 41}] (*Chandler*)
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CROSSREFS
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Cf. A126260, A126261.
Sequence in context: A002790 A108951 A108435 this_sequence A080499 A072513 A022404
Adjacent sequences: A126259 A126260 A126261 this_sequence A126263 A126264 A126265
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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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