Haskell: Lucas Carmichael number generator

LucasCarmichaelNumbers.hs

-- Lucas Carmichael Numbers
--
-- inspired by the Youtube channel Numberphile
-- episode https://www.youtube.com/watch?v=yfr3BIk6KFc
-- "Something special about 399 (and 2015)"
--
-- by [email protected], jan 2015

import Data.Numbers.Primes

isAllFactors :: (Integral a) => a -> [a] -> Bool
isAllFactors n = all (\f -> mod n f == 0)

isSquareFree :: (Integral a) => a -> Bool
isSquareFree n = 
    let pfs = primeFactors n
    in
        all (\p -> mod n (p^2) /= 0) pfs

isLC :: (Integral a) => a -> Bool
isLC n = 
    let pfs = primeFactors n
        n'  = n + 1
        fs' = map (+ 1) pfs
    in
        odd n 
        && not (isPrime n)
        && isSquareFree n
        && isAllFactors n' fs'

lcNumbers :: [Integer]
lcNumbers = filter isLC [3..]

main = do
    putStrLn "Lucas Carmichael numbers less than 100 000"
    print $ takeWhile (<100000) lcNumbers
    putStrLn "Is 3235967 a LC number? "
    print $ isLC 3235967