A035120 Discriminants of real quadratic number fields with class number >= 2.

40, 60, 65, 85, 104, 105, 120, 136, 140, 145, 156, 165, 168, 185, 204, 205, 220, 221, 229, 232, 257, 264, 265, 273, 280, 285, 296, 305, 312, 316, 321, 328, 345, 348, 357, 364, 365, 377, 380, 385, 401, 408, 424, 429, 440, 444, 445, 456, 460, 465, 469, 473

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• easy

References

• H. Cohen, Advanced Topics in Computational Number Theory, Springer, 2000, p. 534.
• H. Hasse, Number Theory, Springer-Verlag, NY, 1980, p. 576.

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• X.-F. Roblot and Igor Schein, Hilbert class field of totally real fields of degree 2, 3 and 4.
• Eric Weisstein's World of Mathematics, Class Number

Crossrefs

Cf. A003656, A094619.

Programs

Mathematica

Select[Range[500], NumberFieldDiscriminant[Sqrt[#]] == # && NumberFieldClassNumber[Sqrt[#]] >= 2 & ] (* Jean-François Alcover, Jul 04 2013 *)

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), May 15 2002