Question

Is the language L = {a^pb^qc^r | p,q,r >= 1 and r =pq} context free?

Answer 1

Using this rule "A language expression which involves counting and comparison of three or more variables independently is not context free language, as stack allows comparison of only two variables at a time."

here we have r=pq constraint which involves 3 independent variables p,q,r so it is not context free language.