A216881 Primes p such that x^7 = 3 has a solution mod p.

2, 3, 5, 7, 11, 13, 17, 19, 23, 31, 37, 41, 47, 53, 59, 61, 67, 73, 79, 83, 89, 97, 101, 103, 107, 109, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 199, 223, 227, 229, 233, 241, 251, 257, 263, 269, 271, 277, 283, 293, 307, 311, 313, 317

Offset: 1

Author

Vincenzo Librandi, Sep 19 2012

Keywords

• nonn
• easy

Comments

Complement of A042969 relative to A000040.

Differs from A042966 first at index 98. - R. J. Mathar, Mar 13 2013

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Programs

Magma

[p: p in PrimesUpTo(500) | exists(t){x: x in ResidueClassRing(p) | x^7 eq 3}];

Mathematica

ok[p_] := Reduce[Mod[x^7 - 3, p] == 0, x, Integers] =!= False; Select[Prime[Range[150]], ok]