## AI coordinated motion – drift offset

I'm reading Ian Milligton's book on AI in the game

On page 150 he introduces the drift offset.

I do not understand how it works:

1) Imagine I have a formation with 2 possible positions (relative to the anchor): (-1, -1) and (1, -1)

2) The drift offset calculated from this information is (0, -1)

3) My anchor starts at position (1,0), has no speed and is in the center of mass of my formation

4) So if I follow the algorithm, my slots are (-1,1) and (1,1).

5) My anchor will stay at (1.0) as this is the center of gravity of the formation

6) I add a new slot (0, -2)

7) Follow the algorithm, drift offset is (0, -2). New slot position: (-1,2) – (1,2) and (0,0)

8) The anchor point is at (0.4 / 3), so it moves

As you saw, when I was doing the algorithm, when I understood my anchor drift, do you know what I'm doing wrong?

Many Thanks

## Combinatorics – Formula for the product of sums of pairwise co-ordinated dividers of \$ n \$.

Can we develop a formula for?

$$r (n) = prod_ { begin {array} {c} x, y mid n \ (x, y) = 1 end {array}} (x + y)$$

In words, this is the product of the sums of all coprime pairs of divisors of $$n$$,

For example
$$r (12) = (1 + 2) (1 + 3) (1 + 4) (1 + 6) (1 + 12) (2 + 3) (3 + 4) = 191100$$

There is some information on the number of coprime divisor pairs (A063647).