You can use an L-system to generate the fractal. F denotes move forward one unit, + rotate left 90 degrees, - rotate right 90 degrees.
Level 0
starting from top of leftmost edge pointing east
F+F-F+F -F- F+F-F+F -F- F+F-F+F -F- F+F-F+F -F-
=:
L(0) -F-
Level 1
starting from 1/3 of the way down the rightmost edge of the center square (1/3 size) pointing east
F+F-F+F -F- F+F-F+F -F- F+F-F+F -F- F+F-F+F +F-F+
F+F-F+F -F- F+F-F+F -F- F+F-F+F -F- F+F-F+F +F-F+
F+F-F+F -F- F+F-F+F -F- F+F-F+F -F- F+F-F+F +F-F+
F+F-F+F -F- F+F-F+F -F- F+F-F+F -F- F+F-F+F +F-F+
=
L(0) +F-F+ L(0) +F-F+ L(0) +F-F+ L(0) +F-F+
=:
L(1) +F-F+
Level 2
starting from 1/3 of the way down the rightmost edge of the center square (1/7 size) pointing east
L(1) +F-F+ L(1) +F-F+ L(1) +F-F+ L(1) +F-F+
=:
L(2) +F-F+
Level 3 and beyond, similarly
L(n) +F-F+ L(n) +F-F+ L(n) +F-F+ L(n) +F-F+
=:
L(n+1) +F-F+