Frank fills a square grid (similar to a scrabble board) with blank tiles. He marks each of the tiles along the bottom edge with a 0, and marks the Lth tile (starting along the bottom) along the left edge L-1.
Continuing to the lower left hand corner of unmarked tiles and progressing upward and right, Frank next marks each tile with the average of the markings immediately below and immediately to the left.
Show that the marking on the A+1th tile along the diagonal is given by:
(2A+1)! / (A!2 22A+1)
