1.
If n∈Nn \in \mathbb{N} and nn is even, then 11!(n−1)!+13!(n−3)!+15!(n−5)!+⋯+1(n−1)!1!\frac{1}{1!(n-1)!} + \frac{1}{3!(n-3)!} + \frac{1}{5!(n-5)!} + \cdots + \frac{1}{(n-1)!1!} equals: