  Let $m,k$ be fixed positive integers. Determining the generating function for
the number of tilings of an $m\times n$ rectangle by $k\times 1$ rectangles is
a long-standing open problem to which the answer is only known in certain
special cases. We give an explicit formula for this generating function in the
case where $m<2k$. This result is used to obtain the generating function for
the number of tilings of an $m\times n \times k$ box with $k\times k\times 1$
bricks.
