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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A072155 Denominator of Sum_{k=1..n} phi(k)/k. 7
 1, 2, 6, 3, 15, 5, 35, 70, 210, 210, 2310, 770, 10010, 10010, 30030, 15015, 255255, 255255, 4849845, 4849845, 4849845, 4849845, 111546435, 37182145, 37182145, 37182145, 111546435, 111546435, 3234846615, 3234846615, 100280245065, 200560490130, 200560490130 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS G. C. Greubel, Table of n, a(n) for n = 1..1000 FORMULA Also denominator of Sum_{i=1..n} (mu(i)/i)*floor(n/i). - Ridouane Oudra, Nov 26 2019 EXAMPLE 1, 3/2, 13/6, 8/3, 52/15, 19/5, 163/35, 361/70, 1223/210, ... MAPLE with(numtheory); seq(denom( add(phi(k)/k, k=1..n)), n =1..35); # G. C. Greubel, Aug 25 2019 MATHEMATICA Table[Sum[EulerPhi[k]/k, {k, n}], {n, 40}]//Denominator (* Harvey P. Dale, Jun 08 2017 *) PROG (PARI) a(n) = denominator(sum(k=1, n, eulerphi(k)/k)); \\ Michel Marcus, Jan 26 2015 (Magma) [Denominator( &+[EulerPhi(k)/k: k in [1..n]] ): n in [1..35]]; // G. C. Greubel, Aug 25 2019 (Sage) [denominator( sum(euler_phi(k)/k for k in (1..n)) ) for n in (1..35)] # G. C. Greubel, Aug 25 2019 (GAP) List([1..35], n-> DenominatorRat( Sum([1..n], k-> Phi(k)/k) ) ); # G. C. Greubel, Aug 25 2019 CROSSREFS Cf. A071708 (numerators), A250031, A250032, A250034. Sequence in context: A055773 A111866 A251753 * A094299 A304537 A330252 Adjacent sequences: A072152 A072153 A072154 * A072156 A072157 A072158 KEYWORD nonn,frac AUTHOR N. J. A. Sloane, Jun 28 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.

Last modified February 3 21:17 EST 2023. Contains 360045 sequences. (Running on oeis4.)