Bonjour, For p prime, sigma(p) - phi(p) = 2. For m composite, sigma(m) - phi(m) > sqrt(m), so a convenient bound for m for "Least number m such that sigma(m) - phi(m) = n " is n^2. The previous proposed (n/4)^2 is not sufficient (for example with A071390(35) = 289). Cordialement, Bernard