  For a finitely generated group $\Gamma$ denote by $\mu(\Gamma)$ the growth
coefficient of $\Gamma$, that is, the infimum over all real numbers $d$ such
that $s_n(\Gamma)<n!^d$. We show that the growth coefficient of a virtually
free group is always rational, and that every rational number occurs as growth
coefficient of some virtually free group. Moreover, we describe an algorithm to
compute $\mu$.

Group Theory