A230375 Squarefree numbers congruent to 2 or 3 mod 4.

2, 3, 6, 7, 10, 11, 14, 15, 19, 22, 23, 26, 30, 31, 34, 35, 38, 39, 42, 43, 46, 47, 51, 55, 58, 59, 62, 66, 67, 70, 71, 74, 78, 79, 82, 83, 86, 87, 91, 94, 95, 102, 103, 106, 107, 110, 111, 114, 115, 118, 119, 122, 123, 127, 130, 131, 134, 138, 139, 142, 143

Offset: 1

Author

Colin Barker, Oct 17 2013

Keywords

• nonn

Comments

Also numbers such that the discriminant of the quadratic field Q(sqrt(n)) equals 4n. - Michel Marcus, Nov 26 2013

The asymptotic density of this sequence is 4/Pi^2 (A185199). - Amiram Eldar, Feb 23 2021

Links

• Colin Barker, Table of n, a(n) for n = 1..1000
• Wikipedia, Quadratic field.

Crossrefs

Cf. A039955, A039957, A185199.

Programs

Mathematica

Select[Range[200],SquareFreeQ[#]&&MemberQ[{2,3},Mod[#,4]]&] (* Harvey P. Dale, Feb 04 2015 *)

PARI

s=[]; for(n=1, 200, if(issquarefree(n) && n%4!=1, s=concat(s, n))); s