Count Different Palindromic Subsequences

Given a string s, return the number of distinct palindromic subsequences in s. Two subsequences are considered different if their resulting strings are different (regardless of chosen indices). Note: This is a hard DP problem that requires careful deduplication to avoid over-counting. Example Input: "bccb" Output: 6 Distinct palindromic subsequences include: "b", "c", "bb", "cc", "bcb", "bccb" Constraints 1 <= len(s) <= 1000 s consists of lowercase letters The answer can be large; apply modulo if required by the interviewer. Example Input bccb Output 6