%I #9 Mar 31 2024 15:07:29

%S 5,7,23,29,31,37,47,53,61,71,101,103,109,127,149,151,157,167,173,181,

%T 191,197,223,239,263,269,271,277,293,317,349,359,367,383,389,397,421,

%U 461,479,503,509,541,557,607,613,647,653,661,677,701,719,733,743,751,757,773,797

%N Primes for which -18 is a primitive root.

%H Vincenzo Librandi, <a href="/A105890/b105890.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Pri#primes_root">Index entries for primes by primitive root</a>

%t pr=-18; Select[Prime[Range[200]], MultiplicativeOrder[pr, # ] == #-1 &]

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Apr 24 2005