Class summation, shortest row

import math
d=0
n=int(input())
for i in range(n+1):
    d+=math.factorial(i)
print(d)

math.factorial() Directly calculate the hierarchical value , If you really can't remember or understand, use this first 

import math
d=1
n=int(input())
for i in range(1,n+1):
    j=1
    for b in range(1,i+1):
        j*=b# Multiply internal loops 
    d+=j
print(d)

There is no function call