As I was solving a math problem, I stumbled upon a question:
What conditions must $a,b,c,d,e$ meet for $n$ to be a natural number?
(Frankly speaking, I would like all but one of $a,b,c,d,e$ to be equal to $1$, but I do not know how to prove it.)
Here it is:
$$n=\frac{bcde+cde+de+e+1}{abcde-1}$$