From Wikipedia, the free encyclopedia:

 A happy number is defined by the following process:
 Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals   1   (where it will stay),   or it loops endlessly in a cycle which does not include   1.   


 Those numbers for which this process end in   1   are       happy   numbers,   
 while   those numbers   that   do   not   end in   1   are   unhappy   numbers. 


Task

Find and print the first   8   happy numbers.

Display an example of your output here on this page.



See also

   The OEIS entry:   The     happy numbers:   A007770
   The OEIS entry:   The unhappy numbers;   A031177


import Data.Char (digitToInt)
import Data.Set (member, insert, empty)
 
isHappy :: Integer -> Bool
isHappy = p empty
  where
    p _ 1 = True
    p s n
      | n `member` s = False
      | otherwise = p (insert n s) (f n)
    f = sum . fmap ((^ 2) . toInteger . digitToInt) . show
 
main :: IO ()
main = mapM_ print $ take 8 $ filter isHappy [1 ..]