References Cited: [307, 588, 673, 682, 690, 692, 1071, 1181, 1416, 1557, 1857, 1939, 2156, 2157, 2158, 2186, 2204, 2654, 2807, 2816] 4.2.1 Definition Given a positive integer r define t(r) = f(r)/r, where f is Euler’s function.