A hard Putnam problem and its elegant solution

3Blue1Brown · Explainer · YouTube title: The hardest problem on the hardest test

Why it's here

HN fans list it among their favorite 3Blue1Brown videos for showing how mathematical problem solving actually unfolds.

What it covers

3Blue1Brown walks through a very hard Putnam competition problem and its elegant solution, emphasizing the visual intuition and the thought process behind solving it.