0  (0,)
1  (1, 6)
2  (2, 15)
3  (3, 4)
4  (5,)
5  (7,)
6  (8,)
7  (9,)
8  (10,)
9  (11, 18)
10  (12, 20)
11  (13,)
12  (14,)
13  (16,)
14  (17, 19)
15  (21,)
16  (22,)