How to Solve Longest Subsequence Repeated k Times Problem

You are given a string s of length n, and an integer k. You are tasked to find the longest subsequence repeated k times in string s. A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters. A subsequence seq is repeated k times in the string s if seq * k is a subsequence of s, where seq * k represents a string constructed by concatenating seq k times. Return the longest subsequence repeated k times in string s. If multiple such subsequences are found, return the lexicographically largest one. If there is no such subsequence, return an empty string.