Table of contents16.1 The Function \phi(n)16.2 A Further Proof of Theorem 6316.3 The Mobius Function16.4 The Mobius Inversion Formula16.5 Further Inversion Formulae16.6 Evaluations of Ramenujan’s Sum16.7 The Functions d(n) and \sigma_k(n)16.8 Perfect Numbers16.9 The Function r(n)16.10 Proof of the Formula for r(n)16.1 The Function ϕ(n) 16.2 A Further Proof of Theorem 63 16.3 The Mobius Function 16.4 The Mobius Inversion Formula 16.5 Further Inversion Formulae 16.6 Evaluations of Ramenujan’s Sum 16.7 The Functions d(n) and σk(n) 16.8 Perfect Numbers 16.9 The Function r(n) 16.10 Proof of the Formula for r(n)