“Identical” is a term basically applicable to a pair (of datasequences in this case).
If one sequence is identical with more than one other, you can count the multitude for the specifice sequence, but not for all the sequences as a whole.
Therefore I read your question as “…want to decide which other sequences are identical to any given one…”.
The classes of identical sequences may then also be evaluated for the numbers of their members.
Of course, this cannot be done by a single formula. (Except, probably, resorting to a custom array-function.)
You may want to study the attached example.
ask251515countIdenticalColumnsPerClass_1.ods