A029702 Q(sqrt(n)) has class number 2.

10, 15, 26, 30, 34, 35, 39, 42, 51, 55, 58, 65, 66, 70, 74, 78, 85, 87, 91, 95, 102, 105, 106, 110, 111, 114, 115, 119, 122, 123, 138, 143, 146, 154, 155, 159, 165, 174, 178, 182, 183, 185, 186, 187, 190, 194, 202, 203, 205, 215, 218, 221, 222, 230, 238, 246

Offset: 1

Author

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

Keywords

• nonn

Comments

Smallest term that is in A146209 but not this sequence is 79, since Q(sqrt(79)) has class number 3. - Alonso del Arte, Aug 25 2014

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, A029703-A029705, A218038-A218042.

Programs

Mathematica

Select[Range[246], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 2 &] (* Arkadiusz Wesolowski, Oct 22 2012 *)

PARI

A007947(n)={my(p); p=factor(n)[, 1]; prod(i=1, length(p), p[i]); }
{ for (n=2, 10^3,
    if ( n!=A007947(n), next() );
    K = bnfinit(x^2 - n);
    if ( K.cyc == [2], print1( n, ", ") );
); }
/* Joerg Arndt, Oct 18 2012 */