The prime numbers. Implemented with the algorithm in:
Colin Runciman (1997) Lazy Wheel Sieves and Spirals of Primes, Functional Pearl, Journal of Functional Programming, 7(2). pp.219--225. ISSN 0956-7968 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.55.7096