Sierpinski triangle

The following program prints an ASCII art Sierpinski triangle.

N:64
step:{(1_ x[0];x[1],~(*x[0])=(*|x[1]))}
row:{(step/[N-1;(1_ x;1)])[1]}
`0:,/'{:[x;"#";" "]}'' row\[N-1;N#1]

Sample output:

################################                                
# # # # # # # # # # # # # # # #                                 
##  ##  ##  ##  ##  ##  ##  ##                                  
#   #   #   #   #   #   #   #                                   
####    ####    ####    ####                                    
# #     # #     # #     # #                                     
##      ##      ##      ##                                      
#       #       #       #                                       
########        ########                                        
# # # #         # # # #                                         
##  ##          ##  ##                                          
#   #           #   #                                           
####            ####                                            
# #             # #                                             
##              ##                                              
#               #                                               
################                                                
# # # # # # # #                                                 
##  ##  ##  ##                                                  
#   #   #   #                                                   
####    ####                                                    
# #     # #                                                     
##      ##                                                      
#       #                                                       
########                                                        
# # # #                                                         
##  ##                                                          
#   #                                                           
####                                                            
# #                                                             
##                                                              
#