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A003647 Class number of real quadratic forms with discriminant 4n+1.
(Formerly M0084)
1
1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 4, 1, 1, 2, 2, 1, 2, 4, 1, 1, 2, 4, 1, 2, 1, 2, 1, 1, 2, 4, 2, 2, 2, 4, 3, 1, 2, 1, 2, 2, 3, 2, 1, 4, 1, 1, 4, 1, 2, 4, 2, 1, 1, 6, 2, 1, 2, 4, 1, 1, 4, 2, 1, 4, 2, 4, 1, 2, 1, 5, 1, 2, 2, 1, 4, 1, 2, 4, 1, 2, 1, 1, 4, 6, 6, 2, 2, 2, 2, 2, 2, 8, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
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..105.

CROSSREFS

Cf. A003648.

Sequence in context: A214713 A049046 A227945 * A084217 A245548 A025903

Adjacent sequences:  A003644 A003645 A003646 * A003648 A003649 A003650

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mira Bernstein

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)