subsequencesOfSize :: Int -> [a] -> [[a]]
subsequencesOfSize n xs | n > length xs = []
subsequencesOfSize n xs = subsequencesBySize xs !! n where
	subsequencesBySize    []  = [[[]]]
	subsequencesBySize (x:xs) = zipWith (++) ([] : map (map (x:)) next) (next ++ [[]])
		where next = subsequencesBySize xs

main = do
	print $ length $ subsequencesOfSize 3   [1..350]
	print $ length $ subsequencesOfSize 147 [1..150]