We discuss some families of integral positive ternary quadratic forms. Our main example is f (x, y, z) = x 2 + y 2 + 16nz 2 , where n is positive, squarefree, and n = u 2 + v 2 with u, v ∈ Z.
NotationAs in [4], [13], and section 7 of [15], we let the integer sextuple a, b, c, r, s, t refer to the quadratic form f (x, y, z) = ax 2 + by 2 + cz 2 + ryz + szx + txy.The Gram matrix for the form is the matrix of second partial derivatives:So our Gram matrix is symmetric, positive definite, and has integer entries. We define our discriminant ∆ as half the determinant of the matrix above, so ∆ = 4abc + rst − ar 2 − bs 2 − ct 2 .All our forms are positive and primitive ( gcd(a, b, c, r, s, t) = 1). Note that we do allow some of r, s, t to be odd at times. When r, s, t are all even, we refer to the form as classically integral.0 ADDRESS: Math.Sci.Res.Inst.,