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A003648 Class number of quadratic forms with discriminant 4n, n == 2,3^( mod 4).
(Formerly M0210)
1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

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=2..105.

CROSSREFS

Cf. A003647.

Sequence in context: A035665 A307833 A083261 * A003642 A100007 A104369

Adjacent sequences:  A003645 A003646 A003647 * A003649 A003650 A003651

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mira Bernstein

STATUS

approved

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Last modified December 12 15:11 EST 2019. Contains 329960 sequences. (Running on oeis4.)