What is the example called, where someone was wrongly convinced of a sequence function because of naive induction.

Question

I remember I have seen a classical example of a mistake, where someone was convinced that a sequence defined somehow had a close form, which did in turn work until some very high $n$. I think the first $n$ to fail was 3 or 5 digits.

Is anyone aware of what is on my mind?

Answer 1

There's a huge list here of apparently true things that eventually fail. Maybe you can find what you were looking for here?