Question 23
Find the number of ways to pave a $1\times10$ block with tiles of sizes $1\times1$, $1\times2$ and $1\times4$, assuming tiles of the same size are indistinguishable. (For example, the following are two distinct ways of using two tiles of size $1\times1$, two tiles of size $1\times2$ and one tile of size $1\times4$. It is not necessary to use all the three kinds of tiles.)
