From 6, 7, 8, 9, 11, 13, 15 and 17, how many arrays can you make up at most?

From 6, 7, 8, 9, 11, 13, 15 and 17, how many arrays can you make up at most?

17-6=11 17-11=6 17-8=9 17-9=8 15-7=8 15-8=7
15-6=9 15-9=6
13-6=7 13-7=6
There are eight