+194 Find an expression for the number of nonnegative integer triples (x, y, z) which are solutions of the equation x + y + z = n, where n is a positive integer.
I believe it has something to do with the hockey stick identity, but I don't know how to solve it T_T
+194 Guys, I ended up figuring it out :)
For those who want to know the answer:
It's n+2 choose 2. That's because you can let n be a number of pieces of candy, and let x, y, and z be the number of candies you give each of 3 kids. Now, applying the Hockey Stick Identity, the answer would be n+3-1 choose 3-1, which is n+2 choose 2.
