A003648 Class number of quadratic forms with discriminant 4n, n == 2,3^( mod 4).
1, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 4, 2, 4, 4, 2, 4, 4, 2, 2, 2, 4, 4, 2, 2, 2, 4, 2, 4, 2, 2, 4, 6, 4, 2, 2, 4, 4, 2, 4, 4, 2, 2, 2, 4, 4, 4, 4, 2, 4, 2, 4, 2, 4, 2, 2, 4, 2, 6, 4, 4, 2, 4, 4, 2, 4, 2, 2, 2, 4, 4, 4, 2, 4, 4, 4, 4, 4, 2, 4, 8, 2, 2, 4, 2, 8, 2, 2, 4, 2, 8, 4, 6, 8, 2, 4, 8, 12, 4, 2, 4, 4, 2
Offset: 2
Keywords
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).
Crossrefs
Cf. A003647.