FYI I wouldn't know how to do fibonacci sequence because I don't know its definition. I could make a guess because it came up as a toy problem before, but because I never actually needed it for anything I'm not super familiar. Compound interview stress and I'd potentially get factorial wrong as well because that's also not something I'd normally implement.

I might recommend, when asking this question, to give the definition with a few example inputs and outputs. That should avoid these types of issues where people are perfectly capable of coding the requested algorithm but aren't mathematicians / toy problem experts