MacMahon, Percy Alexander, 1854-1929 · Cambridge [Eng.] The University press · leaf 35
d. 1634. 14. We can divide the complete set into two portions: (i) those which involve a particular colour, twelve in number ; (ii) the remainder, eight in number, which involve only four colours 1, 2, 3, 4. The first set of 12 is symmetrical in the four colours 1, 2, 3, 4. There are 36… … Fig. 22. For the contact system 0,1,1,1,1 each colour must appear an even number of times upon the boundary, so that the types are fifteen in number: Colours 5 4 1 2 2 4 3 4 I 2 3 1 3 0 10 4:2 0 0 0 0 2 2 0 2 2 8 6 0 2, 2 2 2 0 0 0 0 0 4 6 6 6 2 0 0 0 0 0 2 2 0 4 6 0 0 2 2 0 0 4 4 2 0 4 4 6 0 0 4 2…
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