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A049553 Primes p such that x^21 = 2 has a solution mod p. 2
2, 3, 5, 11, 17, 23, 31, 41, 47, 53, 59, 83, 89, 101, 107, 109, 131, 137, 149, 157, 167, 173, 179, 191, 223, 227, 229, 233, 251, 257, 263, 269, 277, 283, 293, 307, 311, 317, 347, 353, 359, 383, 389, 397, 401, 419, 431, 433, 439, 443, 457, 461, 467, 479, 499 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of A059310 relative to A000040. - Vincenzo Librandi, Sep 14 2012

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..1000

Index entries for related sequences

MATHEMATICA

ok[p_]:= Reduce[Mod[x^21 - 2, p] == 0, x, Integers] =!= False; Select[Prime[Range[150]], ok] (* Vincenzo Librandi, Sep 14 2012 *)

PROG

(MAGMA) [p: p in PrimesUpTo(500) | exists(t){x : x in ResidueClassRing(p) | x^21 eq 2}]; // Vincenzo Librandi, Sep 14 2012

CROSSREFS

Cf. A000040, A059310.

Sequence in context: A103664 A129942 A113239 * A049595 A258039 A107438

Adjacent sequences:  A049550 A049551 A049552 * A049554 A049555 A049556

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified July 13 04:53 EDT 2020. Contains 335673 sequences. (Running on oeis4.)