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%I #12 May 16 2013 02:06:05
%S 410,820,1640,2050,3280,4100,6560,8200,10250,13120,16400,16810,20500,
%T 26240,32800,33620,41000,51250,52480,65600,67240,82000,84050,102500,
%U 104960,131200,134480,164000,168100,205000,209920,256250,262400,268960,328000,336200
%N Numbers n such that phi(n)/n = 16/41.
%C Phi(.)= A000010(.) is the Euler totient function.
%D J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 410, p. 91, Ellipses, Paris 2008.
%H Donovan Johnson, <a href="/A176598/b176598.txt">Table of n, a(n) for n = 1..500</a>
%H H. Fripertinger, <a href="http://www.uni-graz.at/~fripert/fga/k1euler.html">The Euler phi function</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Euler's_phi_function"> Euler's totient function</a>
%F 41n < a(n) <= 205 * 2^n. - _Charles R Greathouse IV_, May 15 2013
%e For n = 410, phi(410)/410 = 160/410 = 16/41, which puts 410 into the sequence.
%p with(numtheory): ii:=1: N0:=40: tabl:=array(1..N0+1): for n from 1 to 540000 do : if 41*phi(n)=16*n then tabl[ii]:= n: ii:= ii+1: fi: od: print(tabl):
%o (PARI) is(n)=eulerphi(n)/n==16/41 \\ _Charles R Greathouse IV_, May 15 2013
%Y Cf. A172344.
%K nonn
%O 1,1
%A _Michel Lagneau_, Apr 21 2010
%E Link to b-file of another sequence removed - _R. J. Mathar_, Oct 20 2010
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