A042969 - OEIS

%I #10 Jun 26 2022 23:37:41

%S 29,43,71,113,127,197,211,239,281,337,379,421,449,463,491,547,617,631,

%T 659,673,701,743,827,911,953,967,1009,1051,1093,1163,1303,1373,1429,

%U 1471,1499,1667,1709,1723,1933,2003,2017,2087,2129,2143

%N Primes p such that x^7 = 3 has no solution mod p.

%C Complement of A216881 relative to A000040. - _Vincenzo Librandi_, Sep 19 2012

%H Vincenzo Librandi, <a href="/A042969/b042969.txt">Table of n, a(n) for n = 1..1000</a>

%t ok[p_]:= Reduce[Mod[x^7 - 3, p] == 0, x, Integers] == False; Select[Prime[Range[800]], ok] (* _Vincenzo Librandi_, Sep 19 2012  *)

%o (Magma) [p: p in PrimesUpTo(2500) | not exists{x : x in ResidueClassRing(p) | x^7 eq 3} ]; // _Vincenzo Librandi_, Sep 19 2012

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_