python1、计算前n个自然数的阶乘之和1!+2!+3!+...+n!的值

以下是三种Python计算前n个自然数的阶乘之和的方法：

方法一：

n = int(input())
b = 1
sum = 0
for i in range(1, n+1):
    b = b * i
    sum += b
print(sum)

方法二：

i = int(input())
sum = 0
if i < 1:
    exit()
else:
    while i > 0:
        b = 2
        c = 1
        while b <= i:
            c = b * c
            b = b + 1
        sum += c
        i = i - 1
print(sum)

方法三：

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

n = int(input())
sum = 0
for i in range(1, n+1):
    sum += factorial(i)
print(sum)