“…, e m }, the subtree number index, denoted by ST (G), is defined as the total number of non-empty subtrees of G. Related to subtrees, a BC-subtree is a subtree in which the distances between any two leaves are even. Similar to the subtree number index, we define the BC-subtree number index, denoted by BST (G), as the total number of non-empty BC-subtrees of G. Both of these indices appeared to have applications in the design of reliable communication network [1], bioinformatics [2], and characterizing structural properties of molecular and graphs [3,4,5,6,7,8,9]. By way of generating functions, Yan and Yeh presented the algorithms of enumerating subtrees of trees [10].…”