An (x+20n) repeater is a repeater that produces a TRUE output on tick *x *(where *x* is an integer between 0 and 19, inclusive), and then every 20 ticks after that. It can be constructed by wiring a counter gate to an odd repeater or an even repeater.

(x+20n) repeaters may be built vertically or horizontally.

To determine the value of x, use the following rules:

For vertical (decrement) repeaters, *x* is equal to the sum of:

- 2 times the number on the counter,
- plus 1 if using an odd repeater
- plus 3 for logic gate delay
- subtract 20 if the total is greater than 20

For horizontal (increment) repeaters, *x* is equal to the sum of:

- 2 times the difference of 9 minus the number on the counter
- plus 1 if using an odd repeater
- plus 3 for logic gate delay
- subtract 20 if the total is greater than 20