Sequences.

It's just the probability of getting Final Attack after you Attack.

it's the Fibonacci sequence!

2 3 5 8 13 21 34 55 89 144

now applying advanced combo:
6 11 29 65 150 337 755 1710 3869 8737

this text file contains all different combinations with probability and the time it takes to fire off a single combination. If you're bored someday.