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%I #8 Sep 08 2022 08:44:53
%S 2,3,5,7,11,43,53,59,61,67,71,103,109,113,127,131,137,163,179,181,191,
%T 223,239,241,251,257,283,307,311,317,349,359,367,419,431,463,479,487,
%U 491,523,541,547,557,593,599,607
%N Primes p such that x^4 = 15 has a solution mod p.
%H Vincenzo Librandi, <a href="/A040130/b040130.txt">Table of n, a(n) for n = 1..1000</a>
%t ok [p_]:=Reduce[Mod[x^4 - 15, 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 15}]; // _Vincenzo Librandi_, Sep 12 2012
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_.
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