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 A072155 Denominator of Sum_{k=1..n} phi(k)/k. 4

%I

%S 1,2,6,3,15,5,35,70,210,210,2310,770,10010,10010,30030,15015,255255,

%T 255255,4849845,4849845,4849845,4849845,111546435,37182145,37182145,

%U 37182145,111546435,111546435,3234846615,3234846615,100280245065,200560490130,200560490130

%N Denominator of Sum_{k=1..n} phi(k)/k.

%e 1, 3/2, 13/6, 8/3, 52/15, 19/5, 163/35, 361/70, 1223/210, ...

%t Table[Sum[EulerPhi[k]/k,{k,n}],{n,40}]//Denominator (* _Harvey P. Dale_, Jun 08 2017 *)

%o (PARI) a(n) = denominator(sum(k=1, n, eulerphi(k)/k)); \\ _Michel Marcus_, Jan 26 2015

%Y Cf. A071708 (numerators), A250031, A250032, A250034.

%K nonn,frac

%O 1,2

%A _N. J. A. Sloane_, Jun 28 2002

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Last modified January 19 17:45 EST 2019. Contains 319309 sequences. (Running on oeis4.)