project-euler/106_special_subset_sums_meta.py

#!/usr/bin/env python3

from math import factorial

def bin(n, k):
    if n < 0:
        return 0
    if n < k:
        return 0
    return factorial(n) // (factorial(n-k) * factorial(k))

n = 12
ms = 0
for k in range(0, n//2 +1):
    ms += bin(n, 2*k) * bin(2*k-1, k+1)

print(ms)