OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
ok [p_]:=Reduce[Mod[x^4 - 20, p]== 0, x, Integers]=!= False; Select[Prime[Range[180]], ok] (* Vincenzo Librandi, Sep 12 2012 *)
PROG
(Magma) [p: p in PrimesUpTo(800) | exists(t){x : x in ResidueClassRing(p) | x^4 eq 20}]; // Vincenzo Librandi, Sep 12 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved