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A069220
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Denominator of Sum_{1<=k<=n, gcd(k,n)=1} 1/k.
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6
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1, 1, 2, 3, 12, 5, 20, 105, 280, 63, 2520, 385, 27720, 6435, 8008, 45045, 720720, 85085, 4084080, 2909907, 3695120, 1322685, 5173168, 37182145, 118982864, 128707425, 2974571600, 717084225, 80313433200, 215656441, 2329089562800
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OFFSET
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1,3
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LINKS
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FORMULA
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G.f. A(x) (for fractions) satisfies: A(x) = -log(1 - x)/(1 - x) - Sum_{k>=2} A(x^k)/k. - Ilya Gutkovskiy, Mar 31 2020
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MATHEMATICA
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Table[s=0; Do[If[GCD[i, n]==1, s=s+1/i], {i, n}]; Denominator[s], {n, 1, 35}]
Table[Denominator[Total[1/Select[Range[n], GCD[n, #]==1&]]], {n, 40}] (* Harvey P. Dale, Jun 07 2020 *)
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PROG
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(PARI) for(n=1, 40, print1(denominator(sum(k=1, n, if(gcd(k, n)==1, 1/k))), ", "))
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CROSSREFS
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Cf. A093600 (numerator of this sum).
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KEYWORD
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nonn,frac
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AUTHOR
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Sharon Sela (sharonsela(AT)hotmail.com), Apr 12 2002
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EXTENSIONS
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STATUS
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approved
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