Puzzles/Statistical puzzles/Summing n

Puzzles | Statistical puzzles | Summing n Given a target sum , you can choose summands each of which is a number, , such that . How many ways are there of doing this? Here the notion of a sum is same as that of a permutation, so two sums are same they contain the same summands in the same order. E.g. and are not the same. While you are at it, whats the answer, if ? solution