An example might be:
Start (power of 2)
- (16 0)
- (16 0 8)
- (16 0 8 12)
(16 0 8 12 4)
- (16 0 8 12 4 14)
(16 0 8 12 4 14 10)
(16 0 8 12 4 14 10 6)
(16 0 8 12 4 14 10 6 2)
- (16 0 8 12 4 14 10 6 2 15)
(16 0 8 12 4 14 10 6 2 15 13)
(16 0 8 12 4 14 10 6 2 15 13 11)
(16 0 8 12 4 14 10 6 2 15 13 11 9)
(16 0 8 12 4 14 10 6 2 15 13 11 9 7)
(16 0 8 12 4 14 10 6 2 15 13 11 9 7 5)
(16 0 8 12 4 14 10 6 2 15 13 11 9 7 5 3)
(16 0 8 12 4 14 10 6 2 15 13 11 9 7 5 3 1)
As an example application, imagine I have 16 pencils in various shades of gray (0=black to 15=lightest). I start drawing on a white sheet of paper with the black (darkest) pencil. I then want to switch to most distinct shade to add to the drawing, so I choose the middle gray (#8) pencil. Later I want to add some new stuff and maintain the greatest difference between all the colors on the drawing (I can't change the colors already used), so I can choose either #12 or #4 -- either way will maintain at least a difference of "4" between shades. The next pencil I should use would be either #4 or #12; whichever I didn't use previously.
With this method of selecting my pencils, I could stop drawing at any time and be assured that I have the greatest distinction possible between colors without knowing ahead of time the number of colors.
Any help would be appreciated. I am posting this in the Scheme forum, but Lisp solutions would be equally welcomed.