Vierkant 28x28 “contain a part which is shifted by half a unit" met de 108 heptomino's. (108 x 7 = 28 x 28 - 28)
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| Helmut Postl-Oostenrijk Vierkant 28x28 “contain a part which is shifted by half a unit" met de 108 heptomino's. (108 x 7 = 28 x 28 - 28) |
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