課程

/后端開(kāi)發(fā)

/Python

/初識(shí)Python

sum?=?0
x?=?1
n?=?1
while?True:
????if?n?>?20:
????????break
????sum?=?sum?+?x
????x?=?x?*?2
????n?=?n?+?1
print(sum)