Euler graph

Euler graph --- эйлеров граф.

The Euler graph is an infinite directed graph such that at level [math]\displaystyle{ n }[/math] there are [math]\displaystyle{ n+1 }[/math] vertices labelled from [math]\displaystyle{ (n,0) }[/math] through [math]\displaystyle{ (n,n) }[/math]. The vertex [math]\displaystyle{ (n,k) }[/math] has [math]\displaystyle{ n+2 }[/math] total edges leaving it, with [math]\displaystyle{ k+1 }[/math] edges connecting it to vertex [math]\displaystyle{ (n+1,k) }[/math] and [math]\displaystyle{ n-k+1 }[/math] edges connecting it to vertex [math]\displaystyle{ (n+1,k+1) }[/math].