@@ -0,0 +1,482 @@
+%22%22%22 Project Euler problem #15. %22%22%22%0A%0Aimport math as mt%0A%0A%0Adef problem():%0A    %22%22%22 Solve the problem.%0A%0A    How many such lattice paths are there through a 20*20 grid?.%0A%0A    http://mathworld.wolfram.com/BinomialCoefficient.html%0A%0A    Answer: 137846528820%0A%0A    %22%22%22%0A    a = 20%0A    b = 20%0A%0A    def binomial_coefficient(n, k):%0A        return mt.factorial(n) / (mt.factorial(n - k) * mt.factorial(k))%0A%0A    return binomial_coefficient(a + b, a)%0A%0A%0Aif __name__ == '__main__':%0A    print problem()%0A

Solve 15.