A particular class of irrational numbers is comprised of the quadratic surds, that is, all irrational numbers x which satisfy equations a[x.sup.2] + bx + c = 0, where coefficients a, b, and c are integers, and a is positive.
The high degree of regularity produced in the binary sequence determined by [-square root of 2] is a reflection of the periodicity of its continued fraction representation, a property shared by all quadratic surds. Continued fractions are also intimately linked to well-formed scales and their duals.