Sloane's Gap
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...
Thanks to http://www.audible.com/numberphile
Here's the paper Dr Grime discusses: http://arxiv.org/pdf/1101.4470.pdf
OEIS: http://oeis.org
Dr Grime: http://singingbanana.com
