This is a simple subtraction with repetition series.
It begins with 20, which is repeated, then 3 is subtracted, resulting in 17, which is repeated, and so on.
Rule = (1st no) (1st no) (1st no - 3 = 2nd no) (2nd no repeat) (2nd no - 3 = 3rd no) (3rd no repeat). . .
Now (20) (20) (20 - 3 = 17) (17) (17 - 3 = 14) (14) (14 - 3 = 11) (11) (11 - 3 = 8) (8)
So the answer is e = 11 8.