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A089684 Numbers n such that 2*phi(n) > n. 3

%I

%S 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,

%T 49,51,53,55,57,59,61,63,65,67,69,71,73,75,77,79,81,83,85,87,89,91,93,

%U 95,97,99,101,103,107,109,111,113,115,117,119,121,123,125,127

%N Numbers n such that 2*phi(n) > n.

%H Vaclav Kotesovec, <a href="/A089684/a089684.jpg">Plot of a(n)/n for n = 1..1000000</a>

%F Asymptotic to c*n with c=2.045...

%t lst={}; Do[If[2*EulerPhi[n]>n, AppendTo[lst, n]], {n, 200}]; lst (* _T. D. Noe_ *)

%t Select[ Range[130], 2EulerPhi[ # ] > # &] (* _Robert G. Wilson v_, Jan 16 2004 *)

%Y Cf. A036798, A067800 (composite n such that 2 phi(n) > n).

%Y Cf. A036798, the missing odd numbers.

%K nonn

%O 1,2

%A Benoit Cloitre, Jan 16 2004

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Last modified April 22 13:02 EDT 2019. Contains 322331 sequences. (Running on oeis4.)