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 A028415 Numerator of Sum_{k=1..n} 1/phi(k). 8

%I

%S 1,2,5,3,13,15,47,25,13,55,281,74,301,311,637,163,1319,453,4117,4207,

%T 4267,4339,48089,49079,9895,10027,10115,10247,72125,73511,369403,

%U 93217,9391,75821,76283,77207,77515,78131,78593,39643,49727,100609,100939,25408,204419

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

%D D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, Section I.27.

%H Robert Israel, <a href="/A028415/b028415.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TotientSummatoryFunction.html">Totient Summatory Function</a>

%e 1, 2, 5/2, 3, 13/4, 15/4, 47/12, 25/6, 13/3, 55/12, 281/60, 74/15, ...

%p map(numer, ListTools:-PartialSums(map(1/numtheory:-phi, [\$1..10000]))); # _Robert Israel_, Apr 16 2019

%t Numerator[Table[Sum[1/EulerPhi[k],{k,n}],{n,50}]] (* _Harvey P. Dale_, Aug 24 2012 *)

%Y Cf. A000010, A048049.

%K nonn,frac

%O 1,2

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

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Last modified May 13 05:02 EDT 2021. Contains 343836 sequences. (Running on oeis4.)