%I
%S 2,3,19,31,59,67,71,79,101,103,107,127,149,151,157,167,179,211,223,
%T 227,229,233,277,307,313,331,349,379,383,397,431,439,457,461,487,523,
%U 547,557,563,577,593,599,607,613
%N Primes p such that x^4 = 19 has a solution mod p.
%H Vincenzo Librandi, <a href="/A040145/b040145.txt">Table of n, a(n) for n = 1..1000</a>
%t ok [p_]:=Reduce[Mod[x^4  19, p]== 0, x, Integers]=!= False; Select[Prime[Range[180]], ok] (* _Vincenzo Librandi_, Sep 12 2012 *)
%o (MAGMA) [p: p in PrimesUpTo(800)  exists(t){x : x in ResidueClassRing(p)  x^4 eq 19}]; // _Vincenzo Librandi_, Sep 12 2012
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_.
