bradyt

sieve :: ([Int], [Int]) -> ([Int], [Int])

sieve p=if (null (snd p))
        then p
        else  sieve ( fst p ++ [ head $ snd p ]
                    , filter (\n -> (/=0) $ mod n $ head $ snd p ) $ tail $ snd p )

sieven :: Int -> [Int]
sieven n = fst $ sieve ([2], [3,5..n])