That URL was stuck for a bit for me, this newer one worked better: http://www.warwick.ac.uk/staff/D.Maclagan/papers/set.pdf http://www.warwick.ac.uk/staff/D.Mac

That URL was stuck for a bit for me, this newer one worked better: http://www.warwick.ac.uk/staff/D.Maclagan/papers/set.pdf http://www.warwick.ac.uk/staff/D.Maclagan/papers/set.pdf Thanks for the tip. Paper from 2003; amusing bit in the tail-end Acknowledgments: We would never have spend so many hours thinking about the “set-Problem” without Joe Buhler’s goading remark that it was shocking that two Berkeley students couldn’t work out the answer. Josh Levenberg helped then by writing our original brute-force program, before we came up with a non-computer proof of “20”.