1.
If nNn \in \mathbb{N} and nn is even, then 11!(n1)!+13!(n3)!+15!(n5)!++1(n1)!1!\frac{1}{1!(n-1)!} + \frac{1}{3!(n-3)!} + \frac{1}{5!(n-5)!} + \cdots + \frac{1}{(n-1)!1!} equals: