it is seen that (u, v, a) is a primitive Pythagorean triple. Without loss of
generality, we may suppose that u is odd and v is even. Then, there exist
positive integers r and s with (r, s) = 1 such that a = r2 + s2, v = 2rs,
u = r2 − s2. Substituting these values of u and v into b2 = 2uv gives