Orders of nut graphs with prescribed vertex and edge orbit counts

Determine, for every r ∈ N and k ≥ r + 1, all graph orders n for which there exists a nut graph of order n with exactly r vertex orbits and k edge orbits.

Background

The paper establishes that for every r ∈ N and k ≥ r + 1, infinitely many nut graphs have r vertex orbits and k edge orbits, thereby resolving existence and infinite realizability at the level of orbit counts. It does not classify the orders of such graphs. The final problem asks for this finer order-by-order realizability characterization.

References

We conclude the paper with another natural problem. Problem 21. For any r E N and k ≥ r + 1, determine all the orders for which there exists a nut graph with r vertex orbits and k edge orbits.

Nut graphs with a prescribed number of vertex and edge orbits  (2502.20201 - Bašić et al., 27 Feb 2025) in Problem 21, Section 5, Conclusion