Clever stuff indeed........
no matter what number you choose ther are only 10 possible answers - every number in the 90,s = 81, every number in the 80's = 72 every number in the 70's = 63 etc etc, so the 10 results will always be - 81, 72, 63, 54, 45, 36, 27, 18 and 9 - and for these the picture is the same - they want you to refresh all the time as each time you refresh the image on the 9 possibles changes
Cheers