https://www.v2ex.com/t/719057

v2.py

l = [2,3,5,7,9]
N = 13

def solve(l, N):
    def helper(l, N, i, ans):
        while i < len(l):
            ans.append(l[i])
            if N == l[i]:
                result.append(ans[:])
            elif N >= l[i] * 2:
                helper(l, N - l[i], i, ans)
            ans.pop()
            i += 1

    result = []
    helper(sorted(l), N, 0, [])
    return result

print(solve(l, N))
# [[2, 2, 2, 2, 2, 3], [2, 2, 2, 2, 5], [2, 2, 2, 7], [2, 2, 3, 3, 3], [2, 2, 9], [2, 3, 3, 5], [3, 3, 7], [3, 5, 5]]