  Refining an estimate of Croot, Dobbs, Friedlander, Hetzel and Pappalardi, we
show that for all $k \geq 2$, the number of integers $1 \leq a \leq n$ such
that the equation $a/n = 1/m_1 + \dotsc + 1/m_k$ has a solution in positive
integers $m_1, \dotsc, m_k$ is bounded above by $n^{1 - 1/2^{k-2} + o(1)}$ as
$n$ goes to infinity. The proof is elementary.
