A014599 Class numbers h(D) of imaginary quadratic fields with discriminant D=1-4*n.

1, 1, 1, 2, 1, 3, 1, 3, 2, 4, 1, 5, 2, 4, 3, 4, 1, 7, 2, 5, 3, 6, 2, 8, 2, 5, 3, 8, 2, 10, 2, 5, 5, 6, 3, 10, 2, 7, 4, 10, 1, 11, 4, 6, 5, 8, 2, 13, 4, 9, 4, 6, 3, 14, 4, 7, 5, 12, 2, 15, 3, 6, 7, 12, 4, 13, 2, 11, 4, 12, 3, 14, 4, 8, 8, 10, 3, 19, 4, 10, 4, 12, 3, 18, 6, 7, 5, 12, 4, 19

Offset: 1

Author

Eric Rains (rains(AT)caltech.edu)

Keywords

• nonn

Comments

Also class number, or number of equivalence classes of positive definite binary quadratic forms of discriminant -(4n-1). - N. J. A. Sloane, May 28 2014

References

• D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989, pages 19 and 224-230. - N. J. A. Sloane, May 28 2014 [Only the squarefree cases appear on pp. 224-230]
• H. Cohen, Course in Computational Alg. No. Theory, Springer, 1993, pp. 514-5.

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..10000

Crossrefs

See A000003 for discriminant -4n.

Programs

PARI

a(n) = qfbclassno(1-4*n)