Add all the A tasks

Task/Arithmetic-Rational/Haskell/arithmetic-rational.hs

@@ -0,0 +1,10 @@
+import Data.Ratio
+
+-- simply prints all the perfect numbers
+main = mapM_ print [candidate
+                   | candidate <- [2 .. 2^19],
+                     getSum candidate == 1]
+  where getSum candidate = 1 % candidate +
+                           sum [1 % factor + 1 % (candidate `div` factor)
+                               | factor <- [2 .. floor(sqrt(fromIntegral(candidate)))],
+                                 candidate `mod` factor == 0]