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.

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

Author

N. J. A. Sloane

Keywords

• nonn
• fini
• full

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.

Crossrefs

A subsequence of A000926.

Cf. A033266, A033268, A033269.

Programs

PARI

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