... algebraic integer, 62 algebraic number, 51 algebraic number theory, 61.71 'almost all' natural numben, 13 'almost all' real numbers, 48,53 Ap&y, R., 54 Apostol, ... quadratic congruence, 27 quadratic fields, 61-73 quadratic forms, 35-92 quadratic irrationals, 48 quadratic residues, 27-34 quaternions, 39 Ramanujan, S., 91 RamanujanSs sum, 17 rational approximations, ... a& apos;= bm'(mod n') for some a& apos;, and now it is easily seen that a, a& apos; have the required property. Fermat's theorem states that if a is any natural number and if p is any...