For an object bouncing off a stationary object, such as a floor, coefficient of restitution, $e = \sqrt{\large \frac{h'}{h}}$

$\Rightarrow$ The height to which it bounces $h' = e^2h$

Similarly, after it rebounds for the nth time, the height to which it rises $h' = e^{2n}h$

Answer: $e^{2n}h$