input: Write a function to calculate an exponential series. The function should take two parameters: x, the base of the exponent, and n, the number of terms to sum. The function should return the sum of the series.
  def exponential_series(x, n):
      sum = 0
      for i in range(n + 1):
          sum += x ** i
      return sum
  
  assert exponential_series(2, 3) == 15
  assert exponential_series(1, 10) == 11
  assert exponential_series(3, 0) == 1
  assert exponential_series(5, 4) == 781
  assert exponential_series(0, 100) == 1
output: def exponential_series(x, n):
      sum = 0
      for i in range(n + 1):
          sum += x ** i
      return sum