Given n \geq 1, let A_{n} denote the set of the first n positive integers. We say that a bijection f: A_{n} \rightarrow A_{n} has a hump at m \in A_{n} \backslash\{1, n\} if f(m)>f(m+1) and f(m)>f(m-1). We say that f has a hump at 1 if f(1)>f(2), and f has a hump at n if f(n)>f(n-1). Let P_{n} be the probability that a bijection f: A_{n} \rightarrow A_{n}, when selected uniformly at random, has exactly one hump. For how many positive integers n \leq 2020 is P_{n} expressible as a unit fraction?