If we exclude isomorphic trees (see Exercise C-8.35), exactly how many proper binary trees exist with exactly 4 leaves? (Draw them)

Below is the exercise C-8.35

C-8.35 Two ordered trees T' and T'' are said to be isomorphic if one of the following holds:

Both T' and T'' are empty.

The roots of T' and T'' have the same number k?0 of subtrees, and the ith such subtree of T' is isomorphic to the ith such subtree of T'' for i = 1,...,k.

Design an algorithm that tests whether two given ordered trees are isomorphic. What is the running time of your algorithm?