Yeah double each time means 2, then 4, then 8, then 16, then 32. How it looks right now is more like it adds one cube each time. So it goes from 2, to 3, to 4, to 5.
I guess you would need a very very large staircase to start with, since if it’s going to double each time it’ll grow exponentially fast if you want to show a cube per rung of the stairs. Unless the also grow sideways? Or maybe the stairs also grow as the cubes double each step?