Main video: https://www.youtube.com/watch?v=Kdsj84UdeYg Go another level deeper with the reaction to the reaction: https://www.youtube.com/watch?v=tD2q2-_5Tyc Matt Parker is Standupmaths: null Tony Várilly-Alvarado: https://math.rice.edu/~av15/ The Parker Square: https://www.youtube.com/watch?v=aOT_bG-vWyg Finite Fields & Return of The Parker Square: https://www.youtube.com/watch?v=FCczHiXPVcA A Special Magic Square: https://www.youtube.com/watch?v=aTSYARnB-3Y Magic Square Party Trick: https://www.youtube.com/watch?v=aQxCnmhqZko Parker Square Tee: https://numberphile.creator-spring.com/listing/the-parker-square NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile Videos by Brady Haran Support us on Patreon: http://www.patreon.com/numberphile Brady's videos subreddit: http://www.reddit.com/r/BradyHaran/ A run-down of Brady's channels: http://www.bradyharan.com/ Sign up for (occasional) emails: http://eepurl.com/YdjL9