Question 137
An $8 \times 8$ square is subdivided into $64$ unit squares like a chessboard. Some of these $64$ unit squares are black, all others are white. Such a configuration is called *spotty* if it contains at least two black unit squares each of which shares an edge with a white unit square to its left or above it.
How many spotty configurations are there?
How many spotty configurations are there?