• Nonaliquots and Robbins Numbers 

    Banks, William David, 1964-; Luca, Florian (Polish Academy of Sciences, Institute of Mathematics, 2005)
    Let '(•) and _(•) denote the Euler function and the sum of divisors function, respectively. In this paper, we give a lower bound for the number of m ≤ x for which the equation m = _(n)−n has no solution. We also show that ...