A Course Schedule Structure
 
We will consider a structure for scheduling courses that will be efficient
and effective in designing a daily course schedule.
Conditions for a Schedule Structure
- 
Each course will meet on exactly three days.
- 
Any two classes will meet on the same day exactly once.
- 
Any two days determine a unique course meeting on those
two days.
- 
There are at least two courses.
Here are two examples:
Notice that each structure has 7 courses and they meet
on 7 days!
| C | E | G |  |  | G | B | C | 
| B | D | G |  |  | G | D | F | 
| A | F | G |  |  | G | A | E | 
| A | D | E |  |  | C | E | D | 
| B | F | E |  |  | D | A | B | 
| A | B | C |  |  | C | A | F | 
| D | F | C |  |  | B | F | E | 
Interesting....these were the same arrangements used for the other stuctures.
But the question we have now is:
Are there any of these course
schedule stuctures that have more or less than 7 courses meeting on 7 days?
That is, is there some special
relation between these course schedule structures and the number 7?