Project Euler 203 (0.02s)

pr203.hs

import Data.Numbers.Primes (primeFactors)
import Data.List (group, nub, sort)
import Control.Arrow ((&&&))
import PECore

squarefree :: Integer -> Bool
squarefree = all ((< 2) . snd) . map ((&&&) head length) . group . primeFactors

numFromPascalTriangles :: Integer -> [Integer]
numFromPascalTriangles n = nub . sort . concat . map (\x -> map (combinations x) $ [0..x]) $ [0..n-1]

main = print . sum . filter squarefree . numFromPascalTriangles $ 51