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A091495 Odd, squarefree n such that n/phi(n) > 2, where phi is Euler's totient function. 3

%I

%S 105,165,195,1155,1365,1785,1995,2145,2415,2805,3003,3045,3135,3255,

%T 3315,3705,3795,3885,3927,4305,4389,4485,4515,4641,4785,4845,4935,

%U 5115,5187,5313,5565,5655,5865,6045,6105,6195,6405,6555,6765,7035,7095,7215

%N Odd, squarefree n such that n/phi(n) > 2, where phi is Euler's totient function.

%C Apparently the squarefree members of the sequence A036798. Note that 105, 165 and 195 are the only terms having 3 prime factors. Also note that all the numbers listed above have 3 as a factor. The smallest number of this form not divisible by 3 is 37182145 = 5*7*11*13*17*19*23.

%H T. D. Noe, <a href="/A091495/b091495.txt">Table of n, a(n) for n=1..1000</a>

%t lst={}; Do[f=FactorInteger[n]; s=Times@@Last/@f; If[s==1&&Times@@(1-1/(First/@f))<1/2, AppendTo[lst, n]], {n, 3, 10000, 2}]; lst

%t Select[Range[1,7301,2],SquareFreeQ[#]&&#/EulerPhi[#]>2&] (* _Harvey P. Dale_, Jul 10 2017 *)

%Y Cf. A036798.

%Y Cf. A118700

%K nonn

%O 1,1

%A _T. D. Noe_, Jan 15 2004

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Last modified June 19 06:47 EDT 2019. Contains 324218 sequences. (Running on oeis4.)