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A067233 Numbers n such that phi(3n+1) = sigma(n). 2

%I

%S 3,21,23,27,30,65,69,95,133,143,203,253,264,413,447,537,618,667,672,

%T 715,863,897,1092,1122,1221,1265,1343,1824,2367,2757,2765,3009,3231,

%U 3471,3605,3683,3741,4088,4195,4578,5838,6295,6533,6747,7689,7701,9548

%N Numbers n such that phi(3n+1) = sigma(n).

%H Donovan Johnson, <a href="/A067233/b067233.txt">Table of n, a(n) for n = 1..1000</a>

%o (PARI) isok(n) = eulerphi(3*n+1) == sigma(n); \\ _Michel Marcus_, Nov 21 2013

%Y Cf. A000010, A000203, A067232.

%K nonn

%O 1,1

%A _Benoit Cloitre_, Feb 20 2002

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Last modified January 24 15:36 EST 2022. Contains 350538 sequences. (Running on oeis4.)