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x=2**(n-1)
n=n+1
sum=sum+x
if n>20：
break
2016-10-01
源自：初识Python 5-6
正在回答
Do you want something like below?
n = 1
sum = 0
while True:
x = 2**(n-1)
n = n + 1
sum = sum + x
if n > 20:
print sum
qq_凮残淩度zkm_03844082 提问者
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