We first check that n=1,2,4 are solutions among n≤4, with m=1,2,5 respectively.
We now assume that n≥5. By Legendre's formula, we know that v2(n!)=n−s2(n) where s2(n) is the number of non-zero digits in the binary representation of n. Thus v2(n!)≤n−1.
If v2(n!)=a<n−1, letting odd(x) denote the odd part of x, we have
odd(n!)+2n−1−a=2m−a
which cannot happen as odd(n!) is odd and the other two terms are even. Hence v2(n!)=n−1 and we must have s2(n)=1⇒n is a power of 2.
Let n=2a. Then a≥3. We claim that odd(n!)≡3(mod8). To see so, we pair up i with n−i=2a−i. If v2(i)<a−2, then odd(2a−i)≡−odd(i)(mod8) and so we have
odd(i)⋅odd(2a−i)≡−odd(i)2≡−1(mod8)
and we have an even number of such pairs. This gives us a product of 1. The remaining i's are of simply 2a−2,2a−1 and 3⋅2a−2, whose odd part multiply to 3 mod 8. Hence the total product is 3 mod 8 as desired. Then
n!+2n−1=2m⇒odd(n!)+1=2m−n−1⇒2m−n−1≡4(mod8)⇒2m−n−1≤4
Thus odd(n!)≤4 which leads to n≤4. So there are no other solutions.