a(3)=77套系统:
123 1-23 1-2-3 1-2-3-13 1-2-3-13-23 1-2-3-13-23-123
2-13 1-2-13 1-2-3-23 1-2-12-13-23 1-2-12-13-23-123
1-123 1-2-23 1-2-12-13 1-2-3-13-123
12-13 1-3-23 1-2-12-23 1-2-3-23-123
12-23 2-3-13 1-2-13-23 1-2-12-13-123
13-23 1-12-13 1-2-3-123 1-2-12-23-123
2-123 1-12-23 1-3-13-23 1-2-13-23-123
3-123 1-13-23 2-3-13-23 1-3-13-23-123
12-123 1-2-123 1-12-13-23 2-3-13-23-123
13-123 1-3-123 1-2-12-123 1-12-13-23-123
23-123 2-12-13 1-2-13-123 2-12-13-23-123
2-12-23 1-2-23-123
2-13-23 1-3-13-123
2-3-123 1-3-23-123
3-13-23 2-12-13-23
1-12-123 2-3-13-123
1-13-123 2-3-23-123
12-13-23 1-12-13-123
1-23-123 1-12-23-123
2-12-123 1-13-23-123
2-13-123 2-12-13-123
2-23-123 2-12-23-123
3-13-123 2-13-23-123
3-23-123 3-13-23-123
12-13-123 12-13-23-123
12-23-123
13-23-123
|