I uploaded this video to YouTube last week but I forgot to make a post here. It’s about a moderately interesting fact about fibonacci numbers that David Cushing told me at MathsJam. I generalised it a bit, so I’ve been meaning to write a post for The Aperiodical or do a snappy video or something like that for ages.

I finally decided last week to just sit down and record myself going through the proof, so here’s that video. I deliberately didn’t prepare beforehand, so it’s just under an hour long and contains a lot of thinking out loud.