m=1 gives no solution, therefore m! is even and n should also be even. Let n=2t⋅s (t and s are positive integers, t≥1 and s is odd). t=1 readily leads to n=2 and m=3.
Now let t≥2. Then m!=2n+n=22t⋅s+2t⋅s≥22t+2t. By induction over t we will show that
22t+2t>(2t−1)!(1)
For t=2, 3 the inequality holds. Assume that it is held for t=k. In order to show that it also holds for k+1 we have to prove that
22+2k22k+1+2k+1≥2k(2k+1)
Since 2n+n22n+2n≥2n−1⟺22n−2≥n(2n−2−1) and 22n−2≥n⋅2n−2 for each positive integer n we get 2n+n22n+2n≥2n−1. By taking n=2k we get 22+2k22k+1+2k+1≥22k−1. Thus, in order to complete the proof we will show that 22k−1≥2k(2k+1) for k≥3. For k=3,4 it is held since 27>42 and 215>72 and for k≥5 we have 22k−1≥24k=22k⋅22k≥2k(2k+1). (1) is proved.
By (1) m!>(2t−1)! and consequently m≥2t. Since 2n+n=22t⋅s+2t⋅s=2t(22t⋅s−t+s) and 2t⋅s≥2t>t we get that 22t⋅s−t+β is odd. Therefore 2t divides the maximal even factor of m! and since m≥2t we get
α=⌊2m⌋+⌊4m⌋+⋯≥t+⌊2t⌋+⌊4t⌋+…
Contradiction since t≥2. Thus, the only solution is: (m,n)=(3,2).