Indecomposable binary quadratic forms (Q919380)

The paper contains the following proposition: Let \(d>4\) and \(d\equiv 2 \bmod 4\) then there does not exist an indecomposable definite binary quadratic form with discriminant \(d\) iff the number of classes in each genus of binary quadratic forms with discriminant \(d\) is 1. Let \(d>4\) and \(d\not\equiv 2 \bmod 4\) then there exists an indecomposable binary form with discriminant \(d\).