As a member of boy scouts I was considering the following problem:
suppose you're organising some kind of olympic games...
*You divide the boys in $2n$ teams (subsets of equal size)
*There are $2n-1$ types of sports which all involve two-team matches
*There will be $2n-1$ time slots: during every time slot every team will play one of the sports in a match against one other team.
*Constraint 1: Every sport can be played by only two teams simultaneously.
*Constraint 2: At the end, every team must have played each type of sport.
*Constraint 3: At the end, every team must have faced all other teams in one match.
The problem is trivially solved for $n=1$, but one can easily check that it cannot be solved for $n=2$ and I have some confidence that neither it can be solved for $n=3$.
Is this problem only solvable for $n=1$?
Is, however, the variant of...
*$2n$ teams, $2n$ sports and $2n$ time slots.
*constraint 1 unchanged
*constraint 2 unchanged
*constraint 3 being relaxed to: "At the end, every team must have faced all other teams in at least one match"
...solvable for all $n \neq 2$ (I have found a solution for $n=1, 3, 4, 5$ but since writing them down is a lengthy business, I'll not give them here unless someone's really interested)?
If so, can you give details of a constructive method to find a solution for a particular $n$?