HA! I just remembered that that proof was posted to /r/math a while back: https://www.reddit.com/r/math/comments/cl20l6/knuth_has_written_up_a_simplified_proof

HA! I just remembered that that proof was posted to /r/math a while back: https://www.reddit.com/r/math/comments/cl20l6/knuth_has_written_up_a_simplified_proof_of_the/ https://www.reddit.com/r/math/comments/cl20l6/knuth_has_writ...