Jiugongge means that every three different numbers add up to the same number, that is, 45/3= 15.

The head and tail add up to the same number, that is, 1+9=2+8=3+7=4+6, and 5 is single, and 5 can only be placed in the middle, so it can be arranged like this:

6 1 8

7 5 3

2 9 4