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## Homework Statement

There are N villages which have to be connected using one-way roads in a manner that for every two villages there exists at least one route to travel from one to another.

How many different solutions are there?

## Homework Equations

This fits pretty well not only into combinatorics but also in a graph theory.

## The Attempt at a Solution

For N=2 there is only 1 trivial solution.

For N=3 there seems to be 15 solutions, but it's done by writing out the combinations and does not lead to general solution.