OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
ok[p_] := Reduce[Mod[x^60 - 2, p] == 0, x, Integers] == False; Select[Prime[Range[80]], ok] (* Vincenzo Librandi, Sep 21 2012 *)
PROG
(Magma) [p: p in PrimesUpTo(400) | not exists{x: x in ResidueClassRing(p) | x^60 eq 2}]; // Vincenzo Librandi, Sep 21 2012
(PARI)
N=10^4; default(primelimit, N);
ok(p, r, k)={ return ( (p==r) || (Mod(r, p)^((p-1)/gcd(k, p-1))==1) ); }
forprime(p=2, N, if (! ok(p, 2, 60), print1(p, ", ")));
/* Joerg Arndt, Sep 21 2012 */
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Klaus Brockhaus, Feb 02 2001
STATUS
approved