%I
%S 2,3,5,19,23,43,47,67,71,97,139,149,163,167,173,191,211,239,241,263,
%T 283,307,311,331,359,379,383,389,409,431,457,461,479,499,503,523,547,
%U 557,571,577,599,601,619,643,647
%N Primes p such that x^4 = 6 has a solution mod p.
%H Vincenzo Librandi, <a href="/A040107/b040107.txt">Table of n, a(n) for n = 1..1000</a>
%t ok [p_]:=Reduce[Mod[x^4 6, p] == 0, x, Integers] =!= False; Select[Prime[Range[200]], ok] (* _Vincenzo Librandi_, Sep 11 2012 *)
%o (MAGMA) [p: p in PrimesUpTo(800)  exists(t){x : x in ResidueClassRing(p)  x^4 eq 6}]; // _Vincenzo Librandi_, Sep 11 2012
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_.
