There are $\displaystyle n$ people and there exist $\displaystyle 2^{n} - 1$ football teams. In each football team we have to choose menager.
BUT: If team $\displaystyle X$ is sum $\displaystyle X = Y\cup Z$ then the menager $\displaystyle X$ is the menager of at least one of teams $\displaystyle Y, Z$
Find the number of possible selections of menager.