Ever heard of this one?
It could lead to something.
Of course, you probably should prove it, rather than just trusting me.
nicholas is stacking blocks. he has 12 red blocks, 15 green blocks, 16 yellow blocks, and 9 blue blocks. He always puts the red on the bottom, green next, then yellow, and finally blue on top. How many different towers could he build? the towers do not have to use all 52 blocks, but they do have at least one of each colour.