pardon110
注意缩进C:\Users\Administrator>py -3
Python 3.7.0 (default, Jun 28 2018, 08:04:48) [MSC v.1912 64 bit (AMD64)] ::
conda, Inc. on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> x1=1
>>> d=3
>>> n=100
>>> x100=x1+(n-1)*d
>>> s=(x1+x100)*n/2
>>> print(s)
14950.0
>>>