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A003652 Class number of real quadratic field with discriminant A003658(n), n >= 2.
(Formerly M0051)
6
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 4, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 3, 2, 1, 1, 1, 1, 1, 1, 1, 3, 2, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 3, 4, 1, 1, 1, 1, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,12

REFERENCES

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

H. Cohen, A Course in Computational Algebraic Number Theory, Springer, 1993, pp. 515-519

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

LINKS

T. D. Noe, Table of n, a(n) for n = 2..3001

S. R. Finch, Class number theory

Steven R. Finch, Class number theory [Cached copy, with permission of the author]

Eric Weisstein's World of Mathematics, Class Number

MATHEMATICA

NumberFieldClassNumber[Sqrt[#]] &/@ Select[Range[500], FundamentalDiscriminantQ] (* G. C. Greubel, Mar 01 2019 *)

PROG

(PARI) for(n=1, 500, if(isfundamental(n) && !issquare(n), print1(quadclassunit(n).no, ", "))) \\ G. C. Greubel, Mar 01 2019

(Sage) [QuadraticField(n, 'a').class_number() for n in (1..500) if is_fundamental_discriminant(n) and not is_square(n)] # G. C. Greubel, Mar 01 2019

CROSSREFS

Sequence in context: A088530 A058060 A088323 * A071625 A309004 A304779

Adjacent sequences:  A003649 A003650 A003651 * A003653 A003654 A003655

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mira Bernstein

EXTENSIONS

Offset corrected by Jianing Song, Mar 31 2019

STATUS

approved

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Last modified November 18 22:31 EST 2019. Contains 329305 sequences. (Running on oeis4.)