A049572 - OEIS

%I #15 Sep 08 2022 08:44:58

%S 2,7,23,47,73,79,89,103,127,151,167,199,223,233,239,257,263,337,359,

%T 367,383,431,439,463,479,487,503,599,607,647,719,727,743,823,839,863,

%U 887,911,919,937,967,983,1039,1063,1087,1103,1217,1223,1249,1279,1289

%N Primes p such that x^40 = 2 has a solution mod p.

%C Complement of A059352 relative to A000040. - _Vincenzo Librandi_, Sep 14 2012

%H R. J. Mathar, <a href="/A049572/b049572.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Pri#smp">Index entries for related sequences</a>

%t ok[p_]:= Reduce[Mod[x^40 - 2, p] == 0, x, Integers] =!= False; Select[Prime[Range[300]], ok] (* _Vincenzo Librandi_, Sep 14 2012 *)

%o (Magma) [p: p in PrimesUpTo(1300) | exists(t){x : x in ResidueClassRing(p) | x^40 eq 2}]; // _Vincenzo Librandi_, Sep 14 2012

%Y Cf. A000040, A059352.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_