No questions with score of 5 or more
Why is non-determinism (Push-down automata) necessary?
How to prove that the Fibonacci sequence is periodic mod 5 without using induction?
Is this problem solvable in polynomial time?
Explicit mu-recursive expression for Ackerman function
Measurable language which is not $\omega$-regular
Unprovable Post correspondence problem instance
What kind of language is needed to recognize an ordered list? [multihead automata, apparently]
The number of states of local automata
Can we check in polynomial time if the language of a DFA is closed against Kleene star?
Regularity of unary languages with word lengths the sum of two resp. three squares
What are the simplest examples of programs that we do not know whether they terminate?