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 A225679 Numerators of phi(n)/n, as n runs through the squarefree numbers (A005117). 4

%I

%S 1,1,2,4,1,6,2,10,12,3,8,16,18,4,5,22,6,28,4,30,20,8,24,36,9,8,40,2,

%T 42,11,46,32,52,8,12,14,58,60,15,48,10,66,44,12,70,72,18,60,4,78,20,

%U 82,64,21,56,88,72,20,23,72,96,100,16,102,16,26,106,108,4

%N Numerators of phi(n)/n, as n runs through the squarefree numbers (A005117).

%C To every fraction taken by the arithmetical function m -> phi(m)/m there is exactly one n such that A225679(n)/A225680(n) is equal to it.

%F a(n) = A000010(A005117(n))/gcd(A000010(A005117(n)),A005117(n)).

%e A005117(5)=6, phi(6)/6=2/6=1/3, so a(5)=1.

%t s = Select[Range[200], SquareFreeQ]; Numerator[EulerPhi[s]/s] (* _T. D. Noe_, May 13 2013 *)

%Y Cf. A225680 (denominators).

%K nonn,easy

%O 1,3

%A _Franz Vrabec_, May 12 2013

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Last modified June 20 12:05 EDT 2019. Contains 324234 sequences. (Running on oeis4.)