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A106031 a(n) is the number of orbits under the action of GL_2[Z] on the primitive binary quadratic forms of discriminant D, where D < 0 is the n-th fundamental discriminant. 0
1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 3, 2, 1, 3, 2, 2, 3, 3, 2, 1, 3, 4, 3, 2, 4, 4, 2, 2, 5, 3, 4, 2, 5, 2, 4, 6, 4, 2, 3, 3, 4, 3, 2, 6, 2, 4, 4, 3, 6, 1, 5, 6, 4, 3, 5, 3, 2, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

A006641 is the same except it is under the action of SL_2[Z].

LINKS

Table of n, a(n) for n=1..60.

S. R. Finch, Class number theory

Steven R. Finch, Class number theory [Cached copy, with permission of the author]

Jens Jonasson, Classes of integral binary quadratic forms, Master's thesis (2001), Appendix B.

EXAMPLE

D = -3, -4, -7, -8, -11, -15, -19, -20, -23, -24, -31, ...,

that is, A003657 negated.

CROSSREFS

Cf. A003657, A006641.

Sequence in context: A323015 A105194 A008335 * A055175 A339930 A307707

Adjacent sequences:  A106028 A106029 A106030 * A106032 A106033 A106034

KEYWORD

nonn

AUTHOR

Steven Finch, May 05 2005

STATUS

approved

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Last modified November 26 17:52 EST 2021. Contains 349343 sequences. (Running on oeis4.)