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You are given a list of n strings strings[0..n-1] (each nonempty). Consider any non-empty subsequence of indices i1 < i2 < ... < ik and form the concatenated string S = strings[i1] + strings[i2] + ... + strings[ik] (where + is string concatenation). Count how many distinct subsequences produce a palindrome S. Return the count of non-empty subsequences whose concatenated string is a palindrome. Constraints - 1 <= n <= 22 - sum of lengths of all strings <= 2000 - strings consist of arbitrary printable characters (you may assume Python str equality and reversal semantics). Notes - Two different index subsequences that give the same concatenated palindrome must be counted separately (we count subsequences, not distinct palindrome values). - The empty subsequence is not allowed. Example Input: (['a','bc','c','b']) Output: 5 Explanation: The valid non-empty subsequences (by indices, 0-based) are: - [0] -> 'a' (palindrome) - [1,3] -> 'bcb' (palindrome: 'bc' + 'b') - [2] -> 'c' (palindrome) - [0,1,3] -> 'abc b' -> 'abcb' (not a palindrome) (example of a non-palindrome) - [1,2,3] -> 'bccb' (palindrome) - [0,1,2,3] -> 'abccb' (not palindrome) Total palindromic subsequences counted: 5 (actual subsequences are [0], [2], [1,3], [1,2,3], and [0,2,3] depending on strings — the example output above corresponds to the correct counting for that input).