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A003649 Class number of real quadratic field Q(sqrt f), where f is the n-th square-free number A005117(n).
(Formerly M0054)
+0
2
1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 2, 2, 1, 1, 4, 1, 1, 1, 1, 2, 1, 1, 3, 2, 4, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 4, 1, 2 (list; graph; listen)
OFFSET

2,6

REFERENCES

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

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

M. Pohst and H. Zassenhaus, Algorithmic Algebraic Number Theory, Cambridge Univ. Press, 1989, p. 432.

LINKS

T. D. Noe, Table of n, a(n) for n=2..6083 (for squarefree numbers < 10000)

S. R. Finch, Class number theory

Index entries for sequences related to quadratic fields

CROSSREFS

Adjacent sequences: A003646 A003647 A003648 this_sequence A003650 A003651 A003652

Sequence in context: A113120 A154843 A062557 this_sequence A003650 A059233 A143898

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com) and Mira Bernstein

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Last modified November 8 20:39 EST 2009. Contains 166234 sequences.


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