Welcome!
As you already may know, rooted trees are the main focus in this post. But before rooted trees, here is the solution to the brain teaser (list all partitions of the integer 8):

TGA involves lots of partition, but in a different style, compared to the picture above. The first number one is not involved in the partitions as a part, but rather acts as a base; the same goes for the first number ones inside brackets, and these brackets are also an additional feature compared to basic partitions.
What comes to rooted trees is the fact that TGA is specifically engineered to generate and enumerate them, with no restrictions applied to functionality by the condition matrix. Even though the Good Will Hunting problem was the one from which the tree generation algorithm was created, rooted trees still act as the most basic type of trees to generate.
I will explain how rooted trees are generated in the next post, but before that, I have one brain teaser for you:
List all partitions of the integer 9
; the solution will be in my next post.