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

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

Author

N. J. A. Sloane, Nov 01 2000

Keywords

• nonn

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

Crossrefs

Cf. A057126, A057125, A057763.

Programs

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 *)