Given an integer n, return a list of all simplified
fractions between 0 and 1 (exclusive) such that the denominator is less-than-or-equal-to
n. The fractions can be in any order.
Example 1:
Input: n = 2 Output: ["1/2"] Explanation: "1/2" is the only unique fraction with a denominator less-than-or-equal-to 2.
Example 2:
Input: n = 3 Output: ["1/2","1/3","2/3"]
Example 3:
Input: n = 4 Output: ["1/2","1/3","1/4","2/3","3/4"] Explanation: "2/4" is not a simplified fraction because it can be simplified to "1/2".
Example 4:
Input: n = 1 Output: []
Constraints:
1 <= n <= 100