Possible Checker Placements
On a 40 by 40 square grid, Victor covers a 1 by 1 square with a checker piece. He is then able to cover the rest of the squares with 533 \( 1 \times 3 \) triminos.
What is the total number of squares on which the checker piece could be placed?
Details and assumptions
The \( 1 \times 3\) trimino consists of 3 squares arranged in a straight row (or column).