input: Write a function to generate the nth number in the Fibonacci sequence using a recursive approach. If n is 0, return 0. If n is 1, return 1. For any other value of n, the function should return the sum of the two preceding numbers in the sequence.
  assert fibonacci_seq(0)==0
  assert fibonacci_seq(1)==1
  assert fibonacci_seq(5)==5
  assert fibonacci_seq(10)==55
  assert fibonacci_seq(15)==610
output: def fibonacci_seq(n):
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return fibonacci_seq(n-1) + fibonacci_seq(n-2)