Dude! It's Pascal's Triangle?
Those "choose" things make the numbers in Pascal's Triangle! I think that's pretty dang cool!
What did we use Pascal's Triangle for?
The coefficients of binomial expansions!
So, we can be a LOT more efficient.
Let's crunch an example and you'll see how it works:
It's even easier to see what's going on when we write out the coefficients:
Here's the form for ONE of these guys: