gistfile1.hs

import Data.Numbers.Primes(primes)
import Data.List(sort, sortBy)

rad :: Integer -> Integer
rad n = product $ f n primes where
    f :: Integer -> [Integer] -> [Integer]
    f 1 _ = []
    f x (y:ys) = if mod x y == 0
        then y : f (remove y x) ys
        else f x ys
    remove factor num = if mod num factor == 0
        then remove factor (quot num factor)
        else num

lista = map (\k -> (k,rad k)) [1..100000]

ordena :: (Ord a, Ord b) => [(a,b)] -> [(a,b)]
ordena = sortBy (\ a b -> compare (snd a) (snd b))

main = putStrLn $ show $ (ordena $ sort lista) !! 9999