-- | Project Euler No. 2
--
-- The prime factors of 13195 are 5, 7, 13 and 29.
--
-- What is the largest prime factor of the number 600851475143 ?
 
primes = 2 : filter ((==1) . length . primeFactors) [3,5..]
primes = 2 : filter ((==1) . length . primeFactors) [3,5..]
primes = 2 : filter ((==1) . length . primeFactors) [3,5..]