A040069 Primes p such that x^3 = 15 has a solution mod p.

2, 3, 5, 7, 11, 17, 23, 29, 31, 41, 47, 53, 59, 67, 71, 79, 83, 89, 101, 107, 113, 131, 137, 149, 167, 173, 179, 191, 197, 223, 227, 229, 233, 239, 251, 257, 263, 269, 277, 281, 283, 293, 311, 317, 331, 347, 353

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Complement of A040070 relative to A000040. - Vincenzo Librandi, Sep 13 2012

Links

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

Crossrefs

Cf. A000040, A040070.

Programs

Magma

[p: p in PrimesUpTo(450) | exists(t){x : x in ResidueClassRing(p) | x^3 eq 15}]; // Vincenzo Librandi, Sep 11 2012

Mathematica

ok [p_]:=Reduce[Mod[x^3 - 15, p] == 0, x, Integers] =!= False;  Select[Prime[Range[180]], ok] (* Vincenzo Librandi, Sep 11 2012 *)

PARI

select(n->ispower(Mod(15, n),3), primes(500)) \\ Charles R Greathouse IV, Sep 11 2012