Stirling number of the first kind

stirling_1.py

@memo  # can be memoized, otherwise comment this line
def stirling1(n,k):
    """Returns the stirling number of the first kind using recursion.."""
    if n == 0 and k == 0:
       return 1
    if k == 0 and n >= 1:
       return 0
    if k > n:
       return 0
    return stirling1(n-1, k-1) - (n - 1) * stirling1(n-1, k)