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Got it, although the more interesting property is that smaller shapes than those in OBS are 4-colorable? (because it is trivially true that if nxk cannot be col
by jules 17y ago
Got it, although the more interesting property is that smaller shapes than those in OBS are 4-colorable? (because it is trivially true that if nxk cannot be colored then larger shapes can't either).
- jrp 17y agoRight, he has apparently solved and proved a short list for OBS3 with the property that X is 3-colorable if and only if X doesn't contain anything from OBS3.