login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069220 Denominator of Sum_{1<=k<=n, gcd(k,n)=1} 1/k. 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
FORMULA
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
MATHEMATICA
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 *)
PROG
(PARI) for(n=1, 40, print1(denominator(sum(k=1, n, if(gcd(k, n)==1, 1/k))), ", "))
CROSSREFS
Cf. A093600 (numerator of this sum).
Also denominators of row sums of A111879/A111880. For the numerators see A111881.
Sequence in context: A147967 A120487 A237873 * A301276 A062957 A288129
KEYWORD
nonn,frac
AUTHOR
Sharon Sela (sharonsela(AT)hotmail.com), Apr 12 2002
EXTENSIONS
More terms from Jason Earls, Apr 14 2002
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)