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 =={{header|Haskell}}==
-<lang haskell>-- Three infinite lists, corresponding to the three definitions in the problem
+<lang haskell>-- Three infinite lists, corresponding to the three
--- statement.
+-- definitions in the problem statement.
 cats1 :: [Integer]
+cats1 =
-cats1 = (\n -> product [n + 2 .. 2 * n] `div` product [1 .. n]) <$> [0 ..]
+  (div . product . (enumFromTo . (2 +) <*> (2 *)))
+    <*> (product . enumFromTo 1) <$> [0 ..]
 cats2 :: [Integer]
+cats2 =
-cats2 = 1 : fmap (\n -> sum $ zipWith (*) (reverse (take n cats2)) cats2) [1 ..]
+:
+  fmap
+    (\n -> sum (zipWith (*) (reverse (take n cats2)) cats2))
+    [1 ..]
 cats3 :: [Integer]
+cats3 =
-cats3 = scanl (\c n -> c * 2 * (2 * n - 1) `div` (n + 1)) 1 [1 ..]
+  scanl
+    (\c n -> c * 2 * (2 * n - 1) `div` succ n)
+    [1 ..]
 main :: IO ()