import Data.List (nubBy)

    refuteGoldbach :: Integer
    refuteGoldbach = head $ [ n
                            | n <- [4,6..]
                            , not $ n `elem` [ p1 + p2 | p1 <- primesTo n, p2 <- primesTo n ]
                            ]
      where primesTo n = takeWhile (< n) $ nubBy isMultiple [2..]
            isMultiple m n = n `rem` m == 0

And then there are pure functions. Every time you compute a function using an input no-one has tried before, you are probably computing something that is not already known. You do this routinely even with a calculator.