The article can have two pay-offs: - People who know some category theory can sharpen their knowledge of it. They can ask followup questions, like does the Fi

The article can have two pay-offs: - People who know some category theory can sharpen their knowledge of it. They can ask followup questions, like does the Fibonacci sequence have a left adjoint? The answer is yes, which is what the top comment on this HN page talks about. - People who don't know category theory might use this to learn some. In which case, we have a case of number theory having applications to category theory rather than the expected converse, which would be category theory having applications to number theory.