where
The sum of the polynomials of these 6 languages is 
We must walk the inclusion-exclusion road. From now on, we may sometimes omit the full language description when it is clear.
The sum of the polynomials of these 15 languages is 
From now on we may group together similar languages under the heading Siblings: often languages which are the reversals of one another.
The sum of the polynomials of these 20 languages is 
The sum of the polynomials of these 15 languages is 
The sum of the polynomials of these 6 languages is 
The polynomial of this language is 
The polynomial describing this language is
