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%I #19 Apr 17 2023 15:35:27
%S 6,12,18,36,72,90,96,108,162,192,432,486,576,702,768,792,924,1152,
%T 1296,1458,2592,2916,3456,3888,4698,5550,6696,7998,8700,10368,10590,
%U 11802,12288,16470,17496,18432,33250,39366,52488,56790,79248,124356
%N Numbers n such that phi(n+1) = 3*phi(n).
%H Donovan Johnson, <a href="/A067143/b067143.txt">Table of n, a(n) for n = 1..1000</a>
%t Position[Partition[EulerPhi[Range[125000]],2,1],_?(#[[2]]==3#[[1]]&), 1,Heads-> False]//Flatten (* _Harvey P. Dale_, Jul 30 2020 *)
%o (PARI) isok(n) = eulerphi(n+1) == 3*eulerphi(n); \\ _Michel Marcus_, Nov 20 2013
%Y Cf. A001274, A050472, A172314.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Feb 19 2002
%E More terms from _Dean Hickerson_, Feb 20 2002
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