A040981 - OEIS

%I #13 Sep 08 2022 08:44:53

%S 11,31,41,61,71,101,151,181,191,211,241,251,271,281,331,401,421,461,

%T 491,541,571,641,661,691,701,751,761,811,821,881,911,941,971,1021,

%U 1031,1051,1091,1151,1171,1181,1201,1231,1301,1361,1471

%N Primes p such that x^5 = 18 has no solution mod p.

%C Complement of A040980 relative to A000040. - _Vincenzo Librandi_, Sep 19 2012

%H Vincenzo Librandi, <a href="/A040981/b040981.txt">Table of n, a(n) for n = 1..1000</a>

%t ok[p_]:= Reduce[Mod[x^5 - 18, p] == 0, x, Integers] == False; Select[Prime[Range[300]], ok]  (* _Vincenzo Librandi_, Sep 19 2012 *)

%o (Magma) [p: p in PrimesUpTo(1500) | not exists{x : x in ResidueClassRing(p) | x^5 eq 18} ]; // _Vincenzo Librandi_, Sep 19 2012

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_.