Some of you may recall my interest in the sequence 1, 2, 4, 8, 14, 24, 36 ... of the number of ways it is possible to interleave N elements chosen from two non-intersecting arithmetic progressions. Another way to view this is as (closely related to) the number of rasterized straight line segments with N+1 pixels, where we light up a pixel if a geometric line intersects its rectangle of screen real estate. The sequence is in OEIS as A005598 ( http://www.research.att.com/~njas/sequences/A005598), and is apparently originally due to Leendert "Leo" Dorst, who wrote about it for his doctoral research, first mentioning it in 1984. Oddly, the corresponding sequence for three arithmetic progressions is, perhaps, not in OEIS yet. The alternative formulation involves polycube models of three-dimensional line segments. Unless I've made a mistake in my enumerations, the sequence begins 1, 3, 9, 27, 75, 189 ... and OEIS has nothing with those elements. Unfortunately, my calculations are all with pen and paper; I haven't written any code to do the counting. So it's quite possible that I blundered, and that OEIS has the sequence after all. Can another funster verify my work? (I have one more element, which I'm holding back to avoid the power of suggestion.) There is an obvious generalization to any number of progressions/dimensions.