input: Write a function to generate the first n elements of the Sierpinski triangle in Python. If the input n is less than 1, the function should generate an empty output. If the input n is valid, the function should print the corresponding Sierpinski triangle.
  
  def sierpinski_triangle(n):
      if n < 1:
          return
      triangle = ["*" * (2**i) for i in range(n)]
      for row in triangle:
          print(row.center(2**n).rstrip())
  
  assert sierpinski_triangle(6)==None
  assert sierpinski_triangle(0)==None
  assert sierpinski_triangle(3)==None
output: def sierpinski_triangle(n):
      if n < 1:
          return
      triangle = ["*" * (2**i) for i in range(n)]
      for row in triangle:
          print(row.center(2**n).rstrip())