Calculate Fibonacci number, in Haskell, with memoization

fibonacciWithMemoization.hs

-- via https://wiki.haskell.org/Memoization
-- P.S. I just realized memoization != memorization ! 
-- https://en.wikipedia.org/wiki/Memoization && https://en.wikipedia.org/wiki/Memorization

memoized_fib :: Int -> Integer
memoized_fib = (map fib [0 ..] !!)
   where fib 0 = 0
         fib 1 = 1
         fib n = memoized_fib (n-2) + memoized_fib (n-1)

-- It's for some online math problem. The organizer does not recommend discussing solutions outside the forum.
main=print $ sum.(filter even) $ takeWhile (<=4000000) $ map memoized_fib [0..]