Spanning forests and special numbers

In this paper, we discuss enumerating some graphs of a special type. New results on the number of spanning forests of graphs playing an important role in information theory are obtained. We consider properties of convergent spanning forests of directed graphs involved in the construction of the quasi-metric of the mean time of the first pass, which is a generalized metric structure closely related to ergodic homogeneous Markov chains. We examine characteristics of spanning root forests and convergent spanning forests of directed and undirected graphs that are used for constructing the matrix of relative forest availability, which is one of the proximity measures of vertices of graphs. The reasonings are illustrated by several simple graph models, including a simple path, a simple cycle, a caterpillar graph, and their oriented analogs.