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A033266 Numbers n such that every genus of binary quadratic forms of discriminant -4n consists of a single class and the class number h(-4n) = 2. 4
5, 6, 8, 9, 10, 12, 13, 15, 16, 18, 22, 25, 28, 37, 58 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989, p. 60.

G. B. Mathews, Theory of Numbers, Chelsea, no date, p. 263.

LINKS

Table of n, a(n) for n=1..15.

PROG

(PARI) ok(n)={my(u=quadclassunit(-4*n).cyc); #u==1 && !select(t->t<>2, u)} \\ Andrew Howroyd, Jun 09 2018

CROSSREFS

A subsequence of A000926.

Cf. A033267, A033268, A033269.

Sequence in context: A242290 A296562 A057854 * A102408 A240564 A189719

Adjacent sequences:  A033263 A033264 A033265 * A033267 A033268 A033269

KEYWORD

nonn,fini,full

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified April 18 12:27 EDT 2019. Contains 322209 sequences. (Running on oeis4.)