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A006643 Class number of quadratic field with discriminant -4n and n runs through numbers congruent to 1 or 2 mod 4.
(Formerly M0225)
+0
2
1, 1, 2, 2, 2, 2, 4, 4, 4, 2, 6, 6, 4, 4, 4, 2, 6, 8, 4, 4, 6, 4, 2, 6, 8, 8, 8, 8, 4, 4, 10, 8, 4, 4, 4, 10, 12, 4, 8, 4, 14, 4, 8, 6, 6, 12, 8, 8, 6, 10, 12, 4, 4, 14, 8, 8, 8, 4, 8, 16, 14, 8, 6, 8, 16, 8, 10, 12 (list; graph; listen)
OFFSET

1,3

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. A006642.

Sequence in context: A085311 A052273 A074912 this_sequence A080217 A157901 A072376

Adjacent sequences: A006640 A006641 A006642 this_sequence A006644 A006645 A006646

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein (mira(AT)math.berkeley.edu)

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Last modified December 9 14:43 EST 2009. Contains 170430 sequences.


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