Prime factorization in Haskell using unfoldr

gistfile1.hs

module PrimeFactorization where

import Data.List

primeFactorsOf :: Int -> [Int]
primeFactorsOf n = (nub . unfoldr (2 `factorOutOf`)) n
  where k `factorOutOf` n
		| n < 2          = Nothing
		| n `mod` k == 0 = Just (k, n `div` k)
		| otherwise      = (k+1) `factorOutOf` n

main :: IO ()
main = print $ primeFactorsOf $ foldl1 lcm [1..20] -- -> [2, 3, 5, 7, 11, 13, 17, 19]