count duplicates every nth cell

Dear all

If I have nth row (Very large number). I want to count the duplicates each 10 cell. For example

For example I have the following set
2
1
1
1
1
1
1
3
2

I need to count the duplicates (taking into account the first duplicate), each 3 cells i.e the output should be
2
1
3


Any suggestions
Thanks in Advance.