You can obtain the coefficients of Hilbert class polynomials. This application is assumed to be called from a program, via the URL:

http://hilbert-class-polynomial.appspot.com/disc

where *disc* is a discriminant of imaginary quadratic field.
The result will be a list in JSON, representing the coefficients in ascending order.
If the polynomial has not been registered (or *disc* does not represents a proper discriminant), the result will be *null*.