Multiplication table for orders of (a,b)(a,b)-Fibonacci sequences with b=−1b=-1

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Let (a,b)(a,b)-Fibonacci sequences be defined by U0=0\mathcal{U}_0=0, U1=1\mathcal{U}_1=1, and Un=aUn−1+bUn−2\mathcal{U}_n=a\mathcal{U}_{n-1}+b\mathcal{U}_{n-2}. Let ω(a,−1)(m)\omega_{(a,-1)}(m) be the number of zeros modulo mm in one period. Negative-bb multiplication conjecture. The multiplication table for ω(a,−1)(lcm⁡[m,n])\omega_{(a,-1)}(\operatorname{lcm}[m,n]) is

ω(a,−1)(n)\ω(a,−1)(m)12112222\begin{array}{c|cc} \omega_{(a,-1)}(n)\backslash\omega_{(a,-1)}(m)&1&2\\\\ \hline 1&1&2\\\\ 2&2&2 \end{array}

Thus the order of the least common multiple is determined by the displayed table. The claim is a proposed extension of the multiplication law for KK-Fibonacci sequences to the case b=−1b=-1; the source gives no resolution.

References

Primary source

Brennan Benfield and Oliver Lippard, “Connecting Zeros in Pisano Periods to Prime Factors of K-Fibonacci Numbers”, arXiv:2407.20048 (2025).

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