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%I #10 Sep 08 2022 08:44:53
%S 13,17,19,23,29,31,37,41,47,73,79,83,89,97,101,107,139,149,151,157,
%T 167,173,193,197,199,211,227,229,233,263,269,271,277,281,293,313,331,
%U 337,347,353,373,379,383,389,397
%N Primes p such that x^4 = 15 has no solution mod p.
%C Complement of A040130 relative to A000040. - _Vincenzo Librandi_, Sep 18 2012
%H Vincenzo Librandi, <a href="/A040136/b040136.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[100]], ok] (* _Vincenzo Librandi_, Sep 18 2012 *)
%o (Magma) [p: p in PrimesUpTo(500) | not exists{x : x in ResidueClassRing(p) | x^4 eq 15} ]; // _Vincenzo Librandi_, Sep 18 2012
%o (PARI) is(n)=isprime(n) && !ispower(Mod(15,n),4) \\ _Charles R Greathouse IV_, Feb 23 2017
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_.
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