'''simple docstring'''

def  _lowerCAmelCase				(				__a      )  ->      int:
     '''simple docstring'''







     if not isinstance(__a			,      __a      ):
          raise ValueError("""double_factorial() only accepts integral values"""      )
     if n < 0:
          raise ValueError("""double_factorial() not defined for negative values"""      )
     return 1 if n <= 1 else n * double_factorial(n - 2      )


if __name__ == "__main__":
      import doctest

      doctest.testmod()

'''simple docstring'''







def   lowerCAmelCase(  a__    :  float      , a__    :  float      , a__    :  int      ):







       '''simple docstring'''






       lowerCamelCase__				   =      [1 / first_term]
       lowerCamelCase__				   =      1 / first_term
       for _ in range(number_of_terms - 1      ):
              first_term += common_difference
              arithmetic_progression.append(a__      )
       lowerCamelCase__				   =      [1 / step for step in arithmetic_progression]
       return sum(a__      )


if __name__ == "__main__":
    import doctest

    doctest.testmod()
    print(sum_of_harmonic_progression(1 / 2, 2, 2))

