2. Induction. Deep in the Amazon lives a remarkable tree that grows downward from the forest canopy. This upside down tree, beloved by both sloths and computer-scientists, is called an s-tree. Mathematically, an s-tree has green and black nodes obeying the following rules. A green node has 2 children. A black node has no children. Example s-tree: 2. Induction. Deep in the Amazon lives a remarkable tree that grows downward from the forest canopy. This upside down tree, beloved by both sloths and computer-scientists, is called an s-tree. Mathematically, an s-tree has green and black nodes obeying the following rules. A green node has 2 children. A black node has no children. Example s-tree