ANSWER Logic Puzzle: What comes next?

Here is my answer to the puzzle that was posted here.
Count the number of occurrences of a particular number in the above sequence along with the number itself.
e.g here 13112221

One 1, One 3, Two Ones, 3 Twos, 1 One
    1           3             11          222          1 
Hence we have..... 1113213211 as the answer.
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