A025023 Numbers whose least quadratic nonresidue (A020649) is 7.

71, 142, 191, 239, 241, 359, 382, 409, 431, 478, 482, 599, 601, 718, 769, 818, 862, 911, 1031, 1198, 1202, 1249, 1321, 1439, 1489, 1538, 1609, 1822, 1871, 2039, 2062, 2089, 2111, 2161, 2281, 2498, 2591, 2642, 2711, 2878, 2879, 2978, 3001, 3119, 3121, 3169

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Quadratic Nonresidue.

Crossrefs

Cf. A020649, A025020, A025021, A025022, A025024, A025025, A025026, A025027, A025028, A025029.

Programs

Mathematica

Select[Range[3200], Min @ Complement[Range[# - 1], Mod[Range[#/2]^2, #]] == 7 &] (* Amiram Eldar, Oct 31 2020 *)

PARI

residue(n,m)=local(r);r=0;for(i=1,floor(m/2),if(i^2%m==n,r=1));r
isA025023(n)=residue(2,n) && residue(3,n) && residue(5,n) && !residue(7,n) \\ Michael B. Porter, Apr 19 2010

PARI

is(n)=issquare(Mod(2,n)) && issquare(Mod(3,n)) && issquare(Mod(5,n)) && !issquare(Mod(7,n)) \\ Charles R Greathouse IV, Jan 24 2020