Odd numbers: 9 8 7, one less than the other, 1.

Even numbers: 7, 6, 5, one less than the other, 65,438+0.

The second way:

1 3 2 6 5 7 ,( 10)

Odd number: 1.25, the difference increases by 2, followed by 1, 3,5,

Even number: 3 6 7, difference increases 1, followed by 3, 4 and 5.