2 633 221 combinations for the upper-left 3x3 puzzle

The number of combinations for a "starting" 3x3 puzzle (the 9 pieces at the upper left corner of the puzzle) is 2 633 221, respecting the game constraints (grey puzzle borders, angles,...) and using the real puzzle pieces.

In this other article, you will find the computation of the first 4x4 puzzle, using only one of the 4 pieces that can match the constraints of the corner. (You will enjoy computing the other combinations with the 3 remaining angles   )