A167798 - OEIS

%I #12 Jan 04 2025 00:37:11

%S 5,7,13,23,25,29,37,47,49,53,61,71,79,101,103,125,149,167,169,173,181,

%T 191,197,199,239,263,269,271,293,311,317,343,349,359,367,373,383,389,

%U 421,461,463,479,487,503,509,529,541,557,599,607,613,625,647,653,661

%N Numbers with primitive root -2.

%C Numbers k such that the largest primitive root of k is k-2. - _Davide Rotondo_, Dec 20 2024

%H Vincenzo Librandi, <a href="/A167798/b167798.txt">Table of n, a(n) for n = 1..1000</a>

%t pr=-2; Select[Range[2,2000], MultiplicativeOrder[pr,# ] == EulerPhi[ # ] &]

%o (PARI) is(n)=if(n%2==0, return(0)); my(p=eulerphi(n)); znorder(Mod(-2, n), p)==p \\ _Charles R Greathouse IV_, Jan 04 2025

%Y Cf. A105874 (primes with primitive root -2).

%K nonn

%O 1,1

%A _T. D. Noe_, Nov 12 2009