Please answer this correctly fill in the missing sequence next to 1

Add 7 to 1, which is 8.
Then, add 8 to 8, which is 16.
This is a "growing pattern."
1 + 7 = 8
8 + 8 = 16
16+ 9 = 25
...
Added amount increases by 1 every time.
So, the blank is 8.