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%I #19 Sep 08 2022 08:46:12
%S 119,527,545,2849,3689,4487,6649,18619,26771,30377,44659,47585,50507,
%T 76997,83021,102167,112463,128933,138773,163877,174437,192881,193115,
%U 198263,217967,236441,243827,244001,254539,268067,282359,287825,298115,345059,410123,464645
%N Numbers n such that phi(n) = 3*phi(n+1).
%H Mauro Fiorentini, <a href="/A256907/b256907.txt">Table of n, a(n) for n = 1..755</a> (all terms with n <= 10^9).
%e phi(545) = 3*phi(546) = 432.
%t Select[Range@ 1000000, EulerPhi@# == 3 EulerPhi[# + 1] &] (* _Michael De Vlieger_, Apr 12 2015 *)
%o (PARI) s=[]; for(n=1, 1000000, if(eulerphi(n)==3*eulerphi(n+1), s=concat(s, n))); s \\ _Colin Barker_, Apr 12 2015
%o (Magma) [n: n in [1..2*10^6] | EulerPhi(n) eq 3*EulerPhi(n+1)]; // _Vincenzo Librandi_, Apr 13 2015
%Y Cf. A171262.
%K nonn
%O 1,1
%A _Mauro Fiorentini_, Apr 12 2015
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