The next number in the series 20 23 28 14 17 22 11
14 and then 19 are the next two numbers in the sequence
Beginning with the 20, the set of rules to get the next 3 terms is:
Add 3 . . . . . 23 Add 5 . . . . . 28 Take half. . . 14 Add 3 . . . . . 17 Add 5 . . . . . 22 Take half. . . 11 Next comes: Add 3 . . . . . 14 Add 5 . . . . . 19
20,23,28,14,17,22,11,
Beginning with the 20, the set of rules to get the next 3 terms is:
Add 3 . . . . . 23
Add 5 . . . . . 28
Take half. . . 14
Add 3 . . . . . 17
Add 5 . . . . . 22
Take half. . . 11
Next comes:
Add 3 . . . . . 14
Add 5 . . . . . 19