input: 
  def sierpinski_triangle(n): 
      """Generates the first n elements of the Sierpinski triangle.
      >>> sierpinski_triangle(6)
      "1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 "
      >>> sierpinski_triangle(3)
      "1 1 1 "
      """
      # Drawing lines for first row 
      for i in range(2**n): 
          print(' ', end=" ") 
      
      # loop for printing n rows 
      for i in range(1, n+1): 
          # bit pattern for first and 
          # last line of each row 
          for j in range(2**(i-1), 2**i): 
              print('1', end=" ") 
          print() 
          
          # inner rows have opposite bit pattern 
          if i > 1: 
              for j in range(2**(i-1)+1, 2**i-1):  
                  print('0', end=" ") 
              print()
  
output:     result = ""
      for i in range(1, n+1):
          for j in range(2**(i-1), 2**i):
              result += '1 '
          result += '\n'
          if i > 1:
              for j in range(2**(i-1)+1, 2**i-1):
                  result += '0 '
              result += '\n'
      return result.strip()