Task
Produce a graphical or ASCII-art representation of a Sierpinski carpet of order   N.



For example, the Sierpinski carpet of order   3   should look like this:

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

The use of the   #   character is not rigidly required for ASCII art.

The important requirement is the placement of whitespace and non-whitespace characters.



Related task

   Sierpinski triangle


package main
 
import (
    "fmt"
    "strings"
    "unicode/utf8"
)
 
var order = 3
var grain = "#"
 
func main() {
    carpet := []string{grain}
    for ; order > 0; order-- {
        // repeat expression allows for multiple character
        // grain and for multi-byte UTF-8 characters.
        hole := strings.Repeat(" ", utf8.RuneCountInString(carpet[0]))
        middle := make([]string, len(carpet))
        for i, s := range carpet {
            middle[i] = s + hole + s
            carpet[i] = strings.Repeat(s, 3)
        }
        carpet = append(append(carpet, middle...), carpet...)
    }
    for _, r := range carpet {
        fmt.Println(r)
    }
}