Special Magic Square

Alex Bellos discusses how the Incans used knots in string (Quipu) to record numbers.Check out Brilliant (get 20% off their premium service): https://brillian...

Magic squares are pretty interesting for Numberphiles any day of the week - but Roger shows us one with extra special "powers".

Professor Roger Bowley works at the University of Nottingham. His drawing of the magic square can be seen at: http://www.flickr.com/photos/numberphile/6477417809

About brown paper: http://periodicvideos.blogspot.com/2012/02/brown-paper-question.html