I wonder if some arrangements of differently-denominated stamps are more handy for postal purposes that others? The lo shu arrangement of the stamps has the convenient property that every value up to 45 pataca can be formed from a contiguous subset of the squares. (Unless I just made a mistake.) Indeed we can ensure that the squared in the subarray form a simply- connected polyomino. E.g., to get 40 pataca, omit the 4 and the 1 or the 2 and the 3. I'm not sure everyone would agree that this is handy, though. Jim On Tuesday, November 4, 2014, Alex Bellos <alexanderbellos@gmail.com> wrote:
http://www.theguardian.com/science/alexs-adventures-in-numberland/2014/nov/0...
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