Matt Parker on the Greatest Maths Mistakes

Why 7 is Weird

Divisibility tests are a lot of fun, and they kept me awake through boring lectures in school. My most fun “discovery” was regarding the number 27, and remind me to tell you about it whenever we meet.

Bertrand’s Paradox, Explained By Numberphile and 3Blue1Brown

… which, by definition, makes this self-recommending!