Sun's conjecture on reciprocal sums over adjacent permutation values

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Let nn be a positive integer and let π∈Sn\pi\in\mathfrak{S}_n be a permutation of {1,…,n}\{1,\ldots,n\}. Sun's reciprocal-sum conjecture. If n>6n>6, there is a permutation π\pi such that

∑k=1n−11π(k)+π(k+1)=1.\sum_{k=1}^{n-1}\frac{1}{\pi(k)+\pi(k+1)}=1.

Moreover, if n>7n>7, there is a permutation π\pi such that

∑k=1n−11π(k)+π(k+1)+1π(n)+π(1)=1.\sum_{k=1}^{n-1}\frac{1}{\pi(k)+\pi(k+1)}+\frac{1}{\pi(n)+\pi(1)}=1.

These assertions are among the conjectures of Sun that the paper explicitly says remain unproved; they ask for both a linear and cyclic permutation arrangement with prescribed reciprocal sum.

References

Primary source

Guo-Niu Han, “On the existence of permutations conditioned by certain rational functions”, arXiv:1910.02662 (2019).

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