I'm having no luck
I'm in a basic sets and logic course, and we're working through induction. I'm supposed to prove: (∀n ∈ N)(Σ r.r! = (n+1)! - 1), where the lower bound is r=1, and the upper is n, and N is the natural numbers. The only thing is that I have no idea how r.r! works. Any help I'd appreciate.