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

1,1

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.

Mathematica

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

Prog

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

Crossrefs

Cf. A039955, A039957, A185199.

Sequence in context: A053438 A042964 A338064 * A062837 A190670 A226115

Adjacent sequences: A230372 A230373 A230374 * A230376 A230377 A230378

Keyword

nonn

Author

Colin Barker, Oct 17 2013

Status

approved