A029704 Q(sqrt(n)) has class number 4.

82, 130, 145, 170, 195, 210, 219, 231, 255, 274, 290, 291, 322, 323, 330, 370, 390, 410, 434, 435, 438, 445, 455, 462, 483, 505, 510, 514, 530, 546, 555, 570, 579, 582, 595, 610, 615, 626, 627, 651, 658, 663, 674, 689, 690, 706, 714, 715, 723, 731, 754, 759, 770

Offset: 1

Author

Paolo Dominici (pl.dm(AT)libero.it)

Keywords

• nonn

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to quadratic fields

Crossrefs

Cf. A003172, A029702-A029703, A029705, A218038-A218042.

Programs

Mathematica

Select[Range[770], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 4 &] (* Arkadiusz Wesolowski, Oct 18 2012 *)

PARI

is(n)=if(issquarefree(n), my(c=bnfinit('x^2-n).cyc); c==[4] || c==[2,2], 0) \\ Charles R Greathouse IV, Oct 18 2012

Extensions

Initial term added by Arkadiusz Wesolowski, Oct 18 2012