Counting Subtrees: Enumerative and Extremal Questions

The subtrees of a tree have been studied from various points of view. In particular, the extremal trees that maximize the number of subtrees were identified for different categories of trees such as binary trees and trees with a given maximum degree. We extend these results to trees with given degree sequences. Furthermore, an ordering of the extremal trees with different degree sequence is provided. This ordering provides a relatively easy way to identify extremal trees. Some of the previously know results follow as corollaries