10 DEFINT A-Z
20 N = 4
30 W = 3^(N-1)
40 S = W
50 L$ = STRING$(W, "#")
60 PRINT L$
70 IF S = 1 THEN END
80 S = S\3
90 P = 1
100 IF P >= W-S GOTO 60
110 P = P+S
120 MID$(L$,P,S) = SPACE$(S)
130 P = P+S
140 GOTO 100