Universal generator-set conjecture for circulant nut graphs

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For a finite set SS of positive integers, call SS universal when Circ⁡(n,S)\operatorname{Circ}(n,S) is a nut graph for every even n≥2max⁡(S)+2n\geq 2\max(S)+2. Here Circ⁡(n,S)\operatorname{Circ}(n,S) is the circulant graph with vertex set {0,1,…,n−1}\{0,1,\dots,n-1\} and edges (i,i±s)(i,i\pm s) modulo nn for s∈Ss\in S.

Universal generator-set conjecture. For each odd t≥3t\geq 3, there exists ptp_t such that Circ⁡(n,{1,…,2t+1}∖{pt})\operatorname{Circ}(n,\{1,\dots,2t+1\}\setminus\{p_t\}) is a nut graph for every even n≥4t+4n\geq 4t+4. For each even t≥4t\geq 4, there exist qtq_t and rtr_t such that Circ⁡(n,{1,…,2t+2}∖{qt,rt})\operatorname{Circ}(n,\{1,\dots,2t+2\}\setminus\{q_t,r_t\}) is a nut graph for every even n≥4t+6n\geq 4t+6.

The conjecture extends the theorem covering many odd values of tt and is motivated by computational evidence through t=1300t=1300 for the remaining odd cases and for even tt; a general proof is not supplied.

References

Primary source

Ivan Damnjanović and Dragan Stevanović, “On circulant nut graphs”, arXiv:2104.10755 (2021).

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