Strongly recommended free excellent MIT Math for high school, undergrads/grads and any self-study learners.
Thanks Prof. Gilbert Strang for the unselfish sharing.
http://ocw.mit.edu/faculty/gilbert-strang/
I find extremely pleasure when I discovered his brilliant lecture notes in “Generating Function” – a Discrete Math technique for computing sequencing using function, and the application in complex Combinatorics. Download here:
Example:
Mathtuition88 