A040148 Primes p such that x^4 = 20 has no solution mod p.

3, 7, 13, 17, 23, 37, 41, 43, 47, 53, 67, 73, 83, 89, 97, 101, 103, 107, 109, 113, 127, 137, 149, 157, 163, 167, 173, 181, 193, 197, 223, 227, 233, 241, 257, 263, 269, 277, 281, 283, 293, 307, 313, 317, 337, 347

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Complement of A040147 relative to A000040. - Vincenzo Librandi, Sep 18 2012

Links

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

Programs

Magma

[p: p in PrimesUpTo(500) | not exists{x : x in ResidueClassRing(p) | x^4 eq 20} ]; // Vincenzo Librandi, Sep 18 2012

Mathematica

ok[p_]:= Reduce[Mod[x^4 - 20, p] == 0, x, Integers] == False; Select[Prime[Range[100]], ok] (* Vincenzo Librandi, Sep 18 2012  *)