We now have a Tumblr: Tumblr: http://numberphile.tumblr.com/ This paper on ebay: http://www.ebay.co.uk/itm/221197137799 More links & stuff in full description below ↓↓↓ Just how hard was the second problem cracked by Will in Good Will Hunting? Matt Damon! And who doesn't love Homeomorphically Irreducible Trees? This video features Dr James Grime - http://singingbanana.com/ Music by Alan Stewart - null NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Videos by Brady Haran Patreon: http://www.patreon.com/numberphile Brady's videos subreddit: http://www.reddit.com/r/BradyHaran/ Brady's latest videos across all channels: http://www.bradyharanblog.com/ Sign up for (occasional) emails: http://eepurl.com/YdjL9 Numberphile T-Shirts: null Other merchandise: https://store.dftba.com/collections/numberphile