%I #17 Jan 31 2018 11:41:05
%S 2,7,17,29,47,53,59,61,67,71,73,89,107,131,137,197,227,229,241,269,
%T 277,283,307,311,313,337,353,359,379,389,401,419,431,433,439,443,449,
%U 457,461,467,479,503,509,557,563,569,599,607,673,677,683,709,727,751,757,761,773
%N Primes with primitive root 31.
%H Vincenzo Librandi, <a href="/A019357/b019357.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 Select[Prime[Range[200]], MultiplicativeOrder[31, # ] == # - 1 &]
%K nonn,easy
%O 1,1
%A _David W. Wilson_