急救，怎么算，具体步骤

k = 1
z=20
sum=0
for j in range(1,21):
for i in range(1,z+1):
k=k*(i)
# print(k,i)
z=z-1
sum=sum+k
k = 1
print(sum)

k=K*(i)应该再缩进一层吧？