I'm just at minute 15 for now, however I can recommend you this link [1] to start with binary trees. The picture also explains why the coefficient of z^3 is 5.

I'm just at minute 15 for now, however I can recommend you this link [1] to start with binary trees. The picture also explains why the coefficient of z^3 is 5. [1] http://cs.lmu.edu/~ray/notes/binarytrees/ http://cs.lmu.edu/~ray/notes/binarytrees/