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Search: id:A000924
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| A000924 |
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Class number of Q(sqrt(-n)), n square-free.
(Formerly M0195 N0072)
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+0
4
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| 1, 1, 1, 2, 2, 1, 2, 1, 2, 4, 2, 4, 1, 4, 2, 3, 6, 6, 4, 3, 4, 4, 2, 2, 6, 4, 8, 4, 1, 4, 5, 2, 6, 4, 4, 2, 3, 6, 8, 8, 8, 1, 8, 4, 7, 4, 10, 8, 4, 5, 4, 3, 4, 10, 6, 12, 2, 4, 8, 8, 4, 14, 4, 5, 8, 6, 3, 6, 12, 8, 8, 8, 2, 6, 10, 10, 2, 5, 12, 4, 5, 4, 14, 8, 8, 3, 8, 4, 10, 8, 16, 14, 7, 8, 4, 6, 8, 10
(list; graph; listen)
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OFFSET
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1,4
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REFERENCES
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Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, pp. 425-430.
D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989, pp. 224-241.
R. A. Mollin, Quadratics, CRC Press, 1996, Appendix D, gives a table for n <= 1999, correcting that of Borevich and Shafarevich.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
S. R. Finch, Class number theory
Index entries for sequences related to quadratic fields
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EXAMPLE
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a(10)=4, since 14 is the 10-th squarefree number and the class number of Q(sqrt(-14)) is 4.
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CROSSREFS
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Values of n run through A005117. Corresponding discriminants give A033197.
Sequence in context: A061498 A106029 A105153 this_sequence A109909 A144387 A030768
Adjacent sequences: A000921 A000922 A000923 this_sequence A000925 A000926 A000927
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein
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EXTENSIONS
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Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Mar 17 2003
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