<image>As shown in the figure: The first figure (①) is a triangle. Connecting the midpoints of its sides, we get the second figure (②), a triangle with smaller triangles inside it. Connecting the midpoints of the sides of the smaller triangles in the second figure (②), we get the third figure (③). How many triangles are there in total in the third figure (③)? Continuing this process, how many triangles are there in total in the nth figure?
