login
A033267
Numbers n such that every genus of binary quadratic forms of discriminant -4n consists of a single class and the class number h(-4n) = 4.
4
21, 24, 30, 33, 40, 42, 45, 48, 57, 60, 70, 72, 78, 85, 88, 93, 102, 112, 130, 133, 177, 190, 232, 253
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==2 && !select(t->t<>2, u)} \\ Andrew Howroyd, Jun 09 2018
CROSSREFS
A subsequence of A000926.
Sequence in context: A111356 A344806 A295692 * A186402 A346294 A330736
KEYWORD
nonn,fini,full
STATUS
approved