Steiner n-center

Steiner [math]\displaystyle{ n }[/math]-center --- [math]\displaystyle{ n }[/math]-центр Штейнера.

The Steiner distance of a set [math]\displaystyle{ S }[/math] of vertices in a connected graph [math]\displaystyle{ G }[/math] is the minimum number of edges in a connected subgraph containing [math]\displaystyle{ S }[/math]. The Steiner [math]\displaystyle{ n }[/math]-eccentricity [math]\displaystyle{ e_{n}(v) }[/math] is the maximum Steiner distance among sets of order [math]\displaystyle{ n }[/math] containing [math]\displaystyle{ v }[/math]. The Steiner [math]\displaystyle{ n }[/math]-center is the set of vertices with the minimum Steiner [math]\displaystyle{ n }[/math]-eccentricity. It is easy to verify that the Steiner 2-eccentricity and 2-center correspond to the eccentricity and center, respectively.