B"A subsequence is a sequence that can be obtained from another sequence by removing some elements without changing the order of the remaining elements. A palindromic sequence is a sequence that is equal to the reverse of itself. You are given a sequence of n integers a_1, a_2, ... , a_n . Any integer value appears in a no more than twice. What is the length of the longest palindromic subsequence of sequence a ? The first line contains a single integer t ( 1 <= t <= 1000 ) -- the number of testcases. Then the descriptions of t testcases follow. The first line of each testcase contains a single integer n ( 1 <= n <= 250 ,000 ) -- the number of elements in the sequence. The second line of each testcase contains n integers a_1, a_2, ... , a_n ( 1 <= a_i <= n ). Any integer value appears in a no more than twice. The sum of n over all testcases doesn't exceed 250 ,000 . For each testcase print a single integer -- the length of the longest palindromic subsequence of sequence a . Here are the longest palindromic subsequences for the example testcases: "...