A057762 Numbers n such that 5 is a square mod n.

1, 2, 4, 5, 10, 11, 19, 20, 22, 29, 31, 38, 41, 44, 55, 58, 59, 61, 62, 71, 76, 79, 82, 89, 95, 101, 109, 110, 116, 118, 121, 122, 124, 131, 139, 142, 145, 149, 151, 155, 158, 164, 178, 179, 181, 190, 191, 199, 202, 205, 209, 211, 218, 220, 229

Offset

1,2

Comments

Numbers not divisible by 3, 8, or 25 and whose prime factors > 5 are congruent to +/- 1 mod 5. - Eric M. Schmidt, Jan 24 2014

Links

T. D. Noe, Table of n, a(n) for n=1..1000

Maple

with(numtheory); [seq(mroot(5, 2, p), p=1..400)];

Mathematica

Prepend[ Select[ Range[300], Reduce[ Mod[5 - k^2, #] == 0, k, Integers] =!= False &], 1] (* Jean-François Alcover, Sep 20 2012 *)
Join[{1, 2, 4, 5}, Select[Range[6, 300], MemberQ[Mod[Range[#]^2, #], 5] &]] (* T. D. Noe, Sep 20 2012 *)

Crossrefs

Cf. A057126, A057125, A057763.

Sequence in context: A167795 A322068 A138048 * A109511 A018339 A328009

Adjacent sequences: A057759 A057760 A057761 * A057763 A057764 A057765

Keyword

nonn

Author

N. J. A. Sloane, Nov 01 2000

Status

approved