adding recursion review question

lectures/08_vector_implementation/README.md

@@ -14,8 +14,11 @@ What is the value of fun(2)?
 
 ```cpp
 int fun(int n) {
-if (n == 4) return n;
+    if (n == 4){
-else return 2*fun(n+1);
+        return n;
+    } else {
+        return 2 * fun(n+1);
+    }
 }
 ```