Fibonomial Lucas-type divisibility conjecture

Let FnF_n denote the Fibonacci numbers, and define the Fibonomial coefficient by

(nk)F=FnFn1Fnk+1FkFk1F1.{n \choose k}_F=\frac{F_nF_{n-1}\cdots F_{n-k+1}}{F_kF_{k-1}\cdots F_1}.

For a prime pp, let pp^* be the least positive integer such that pFpp\mid F_{p^*}, and let

Fp=(1,p,pp,pp2,).\mathcal{F}_p=(1,p^*,p^*p,p^*p^2,\ldots).

Write (n)Fp=(ni)i0(n)_{\mathcal{F}_p}=(n_i)_{i\geq 0} and (k)Fp=(ki)i0(k)_{\mathcal{F}_p}=(k_i)_{i\geq 0}.

Fibonomial Lucas-type divisibility conjecture. If ppp^*\geq p, then

p(nk)Fp(n0k0)F(n1k1)F(n2k2)F.p\mid {n\choose k}_F\quad\Longleftrightarrow\quad p\mid {n_0\choose k_0}_F{n_1\choose k_1}_F{n_2\choose k_2}_F\cdots.

This conjecture proposes that, when the Fibonacci entry point pp^* is at least pp, divisibility of a Fibonomial coefficient by pp is determined by the corresponding digitwise product in the base Fp\mathcal{F}_p. The preceding discussion notes that the analogous relation holds for p=2p=2, while for p<pp^*<p it can fail even to preserve divisibility; the status for the stated range is left open here.

Sources & referencesView supporting material

Primary source

Jeremiah Southwick, “A Conjecture concerning the Fibonomial Triangle”, arXiv:1604.04775 (2016).

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