Add small collatz details

src/3n+1/Main.hs

@@ -1,3 +1,8 @@
+{-
+The Simplest Math Problem No One Can Solve - Collatz Conjecture
+https://youtu.be/094y1Z2wpJg
+-}
+
 import           Control.Monad ()
 import           Debug.Trace   (trace)
 
@@ -7,10 +12,10 @@ f' n = f'' 0 n
     f'' :: Integer -> Integer -> Integer
     f'' i n'
       | n' == 1 = t' i
-      | even n' = t $ f'' (i + 1) (n' `div` 2)
-      | odd  n' = t $ f'' (i + 1) (3*n' + 1)
+      | even n' = t $ f'' (succ i) (n' `div` 2)
+      | odd  n' = t $ f'' (succ i) (3*n' + 1)
       where t   = trace ("i: " ++ show i ++ ", number: " ++ show n')
-            t'  = t'' $ trace ("END: " ++ show n ++ ", length: " <> show i) $ t''
+            t'  = t'' $ trace ("END: " ++ show n ++ ", length: " <> show i) t''
             t'' = trace "\n#######################################################\n"
 
 f :: Integer -> Integer
@@ -21,7 +26,7 @@ f n = s 0 n
       | n == 1 = i
       | even n = s i' (n `div` 2)
       | odd  n = s i' (3*n + 1)
-      where i' = i + 1
+      where i' = succ i
 
 main :: IO ()
 main = print $ map f [2^361..]