Obstacle number two conjecture for gyroelongated bipyramids

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Let XnX_n denote the gyroelongated nn-bipyramid, and let obs⁡out(Xn){\operatorname{{obs}}}_\mathrm{out}(X_n) be its outside obstacle number. Obstacle-number conjecture. If n≥4n\geq 4, then

obs⁡out(Xn)=2.{\operatorname{{obs}}}_\mathrm{out}(X_n)=2.

The paper establishes this for n=4,5,6n=4,5,6 and explains that larger cases were not computationally feasible; the conjecture asserts that no representation using only an outside obstacle exists for every larger nn.

References

Primary source

Leah Wrenn Berman, Glenn G. Chappell, Jill R. Faudree, John Gimbel, Chris Hartman and Gordon I. Williams, “Graphs with obstacle number greater than one”, arXiv:1606.03782 (2017).

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