最难的考试里最难的那道题

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

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

“these videos give a sense of how someone might actually go about thinking through and solving these kinds of problems”