It’s the 100 year centenary of an obscure type of prime number – the Woodall Primes. To celebrate, stand-up mathematician Matt Parker is calling on listeners to search for a new one. Ordinary citizens can already help search for Mersenne Prime numbers by lending computer processing power to GIMPS – the Great Internet Mersenne Prime Search. Matt explains to Tim Harford what a Woodall Prime is, and why it deserves more attention. Also - Making penalty shoot-outs fairer - 60% of penalty shoot-outs are won by the team going first, can this unfairness be overcome? (image Matt Parker / photographer: Steve Ullathorne)