IndependentAlleles.hs

fac n = product [1..n]

combination 0 _ = 1
combination _ 0 = 1
combination n k =
  let fn = fac n
      fk = fac k
      fnk = fac (n - k)
  in fn / (fk * fnk)

bernoulliTrial n k p q =
  (combination n k) * (p ** k) * (q ** (n - k))

main = do
  inputs <- getLine
  let is = (map read $ words inputs) :: [Double]
      gens = head is
      num = last is
      percs = map (\k -> bernoulliTrial (2**gens) k 0.25 0.75) [0..(num - 1)]
  putStrLn $ show (1 - sum percs)