|
%I #15 Sep 29 2020 04:05:38
%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 k such that 2*phi(k) > k.
%H Amiram Eldar, <a href="/A089684/b089684.txt">Table of n, a(n) for n = 1..10000</a>
%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. A000010, A036798, A067800 (composite n such that 2 phi(n) > n).
%Y Cf. A036798, the missing odd numbers.
%K nonn,easy
%O 1,2
%A _Benoit Cloitre_, Jan 16 2004
|
