[Project Euler]Problem 6

Problem 6:
　　The sum of the squares of the first ten natural numbers is,
　　　　12 + 22 + ... + 102 = 385
　　The square of the sum of the first ten natural numbers is,
　　　　(1 + 2 + ... + 10)2 = 552 = 3025
　　Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 方法二

def f2(n):
return ((n+1)*n*(n-1)*(3*n+2))//12