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Euler's ϕ-Function

§ I.1 Elementary inequalities for ϕ

  1. for n ≠ 2 and n ≠ 6
    A.M. Vaidya. An inequality for Euler's totient function. Math. Student 35 (1967), 79-80.
  2. ϕ(n)>n 2/3 for n>30
    D.G. Kendall and R. Osborn. Two simple lower bounds for Euler's function. Texas J. Sci. 17 (1965), No. 3.
  3. If a>6 and n>2, then
    R.L. Goldstein. An inequality for Euler's function ϕ(n). Math. Mag. 40 (1956), 131.
  4. if n is composite
    W. Sierpiński. Elementary theory of numbers. Warsawa, 1964.
  5. for n≥3
    H. Hatalová and T. Šalát. Remarks on two results in the elementary theory of numbers. Acta Fac. Rer. Natur Univ. Comenian. Math. 20 (1969), 113-117.

§ I.2 Inequalities for ϕ(mn)

  1. ϕ(m) ϕ(n)≤ϕ(mn)≤n · ϕ(m); m, n=1, 2, 3, … (Simple consequence of the formula expressing ϕ)
  2. (ϕ(mn))2≤ϕ(m 2) · ϕ(n 2); m, n=1, 2, 3, …
    T. Popoviciu. Gaz. Mat. (Bucureşti), 46 (1940), p. 334.

§ I.3 Relations connecting