Question 4
Solve over positive integers the equation $$
k! = \prod_{i=0}^{n-1} (2^n-2^i) = (2^n-1)(2^n-2)(2^n-4) \dots (2^n-2^{n-1}).
$$
k! = \prod_{i=0}^{n-1} (2^n-2^i) = (2^n-1)(2^n-2)(2^n-4) \dots (2^n-2^{n-1}).
$$
International Mathematical Olympiad 2019 — Official contest Question 4
IMO · International Mathematical Olympiad 2019 — Official contest