A perfect cover.
This is a pretty famous problem that I wanted to share:
In how many ways can 32 2x1 dominoes form a perfect cover of a regular 8x8 chessboard?
Details and Assumptions
A perfect cover of a chess board with dominoes is the scenario where no two dominoes overlap and no domino hangs over the edge of the board. They are arranged in such a way that each domino covers one black square and one white square and the whole chess board is exactly covered by these dominoes.