Gregory–Newton summation identity for signed pancake distances

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Let RkB(n)R_k^B(n) denote the number of signed permutations of size nn whose burnt-pancake distance from the sorted stack is kk. Summation identity conjecture. If k,n≥1k,n\geq1, then

RkB(n)=∑j=1k(∑i=0k−j(−1)i(i+j−1i)(ni+j))RkB(j).R_k^B(n)=\sum_{j=1}^k\left(\sum_{i=0}^{k-j}(-1)^i\binom{i+j-1}{i}\binom{n}{i+j}\right)R_k^B(j).

The identity is observed in the source and is motivated by the assertion that the functions RkB(n)R_k^B(n) are integer-valued polynomials together with the Gregory–Newton interpolation formula. No proof or resolution is supplied, so it remains open.

References

Primary source

Saúl A. Blanco, Charles Buehrle and Akshay Patidar, “On the number of pancake stacks requiring four flips to be sorted”, arXiv:1902.04055 (2019).

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