A216885 Primes p such that x^47 = 2 has a solution mod p.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271

Offset: 1

Author

Vincenzo Librandi, Sep 20 2012

Keywords

• nonn
• easy

Comments

Complement of A059257 relative to A000040.

a(n) = A015919(n+1) up to n=60, and then both sequences start to differ substantially. [Bruno Berselli, Sep 20 2012]

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^47 eq 2}];

Mathematica

ok[p_] := Reduce[Mod[x^47 - 2, p] == 0, x, Integers] =!= False; Select[Prime[Range[100]], ok]