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%I #8 Sep 08 2022 08:44:53
%S 2,5,11,19,31,59,71,79,101,109,131,139,149,151,179,181,191,199,211,
%T 239,251,269,271,311,331,359,379,389,401,409,419,431,439,449,461,479,
%U 491,499,521,541,569,571,599,619
%N Primes p such that x^4 = 5 has a solution mod p.
%H Vincenzo Librandi, <a href="/A040105/b040105.txt">Table of n, a(n) for n = 1..1000</a>
%t ok [p_]:=Reduce[Mod[x^4- 5, 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 5}]; // _Vincenzo Librandi_, Sep 11 2012
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_.
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