A042969 Primes p such that x^7 = 3 has no solution mod p.

29, 43, 71, 113, 127, 197, 211, 239, 281, 337, 379, 421, 449, 463, 491, 547, 617, 631, 659, 673, 701, 743, 827, 911, 953, 967, 1009, 1051, 1093, 1163, 1303, 1373, 1429, 1471, 1499, 1667, 1709, 1723, 1933, 2003, 2017, 2087, 2129, 2143

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Complement of A216881 relative to A000040. - Vincenzo Librandi, Sep 19 2012

Links

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

Programs

Magma

[p: p in PrimesUpTo(2500) | not exists{x : x in ResidueClassRing(p) | x^7 eq 3} ]; // Vincenzo Librandi, Sep 19 2012

Mathematica

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