  Denote by $N_{\ell}(n)$ the number of $\ell$-tuples of elements in the
symmetric group $S_n$ with commuting components, normalized by the order of
$S_n$. In this paper, we prove asymptotic formulas for $N_\ell(n)$. In
addition, general criteria for log-concavity are shown, which can be applied to
$N_\ell(n)$ among other examples. Moreover, we obtain a Bessenrodt-Ono type
theorem which gives an inequality of the form $c(a)c(b) > c(a+b)$ for certain
families of sequences $c(n)$.
