A006642 Class number of quadratic field with discriminant -4n+1. (Formerly M0152)

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

Offset

1,4

References

D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989, pp. 224-241.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..68.

Crossrefs

Cf. A006643.

Sequence in context: A128133 A032434 A002347 * A376239 A332435 A361744

Adjacent sequences: A006639 A006640 A006641 * A006643 A006644 A006645

Keyword

nonn

Author

N. J. A. Sloane, Mira Bernstein

Status

approved