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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
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.
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.
Sequence in context: A242290 A296562 A057854 * A355641 A363701 A353193
KEYWORD
nonn,fini,full
STATUS
approved