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Problems known to be open in the literature and any problem that, after being posed, is decided to be open by the community.

48 votes

Are there any open problems left about DFAs?

Here's a very simple decision problem about DFA's. Given a DFA M, does M accept the base-2 representation of at least one prime number? Currently, we don't even know if this problem is recursively …
Jeffrey Shallit's user avatar