Diregular digraph

Diregular digraph --- дирегулярный орграф.

Let [math]\displaystyle{ \rho \in \{1,2, \ldots\} }[/math]. A digraph [math]\displaystyle{ D }[/math] is called [math]\displaystyle{ \rho }[/math]-diregular if every vertex of [math]\displaystyle{ D }[/math] has the degree pair [math]\displaystyle{ (\rho,\rho) }[/math]. Hence, if a [math]\displaystyle{ \rho }[/math]-diregular oriented graph has [math]\displaystyle{ n }[/math] vertices, then [math]\displaystyle{ \rho \leq \frac{n-1}{2} }[/math]. Moreover, a digraph is called diregular if it is [math]\displaystyle{ \rho }[/math]-diregular for some [math]\displaystyle{ \rho }[/math].