Haskell Fibonacci Prime Finder

gistfile1.hs

squareRoot :: Integer -> Integer
squareRoot = floor . sqrt . (fromIntegral :: Integer -> Double)

isPrime :: Integer -> Bool
isPrime 1 = False
isPrime x = testDown x (squareRoot x) where
  testDown a 1 = True
  testDown a n
    | a `mod` n == 0 = False
    | otherwise = testDown a (n-1)

fib :: [Integer]
fib = seededFib 1 1 where
  seededFib n n1 = n : seededFib n1 (n + n1)