English

The size of $k$-th order generalized Fibonacci cubes

Combinatorics 2026-01-27 v1

Abstract

Let k2k\geq2. Then the kk-th order Fibonacci cube Γn(k)\Gamma^{(k)}_{n} is the subgraph of the hypercube QnQ_{n} induced by vertices without kk consecutive 11s. The case k=2k=2 corresponds to the classic Fibonacci cube Γn\Gamma_{n}. There are three kinds of calculation formulas of the size of Γn\Gamma_{n}: the iteration form E(Γn)=E(Γn1)+E(Γn2)+Fn|E(\Gamma_{n})|=|E(\Gamma_{n-1})|+|E(\Gamma_{n-2})|+F_{n} (Hsu, 1993), %iteration form the convolution form E(Γn)=i=1nFiFni+1|E(\Gamma_{n})|=\mathop{\sum}\limits_{i=1}^{n}F_{i}F_{n-i+1} (Klav\v{z}ar, 2005) %convolution form and the linear form E(Γn)=nFn+1+2(n+1)Fn5|E(\Gamma_{n})|=\frac{nF_{n+1}+2(n+1)F_{n}}{5} (Munarini et al., 2001). %linear form Belbachir and Ould-Mohamed (2020) studied the iteration and convolution formulas of the size of Γn(3)\Gamma^{(3)}_{n}. Very recently, Mollard (2025) deduced the iteration formula of the size of Γn(k)\Gamma^{(k)}_{n} for k2k\geq2. In this paper, we give the the formulas of convolution and linear forms of E(Γn(k))|E(\Gamma^{(k)}_{n})| for all k2k\geq2. Specifically, we obtain the formula of E(Γn(k))|E(\Gamma^{(k)}_{n})| in terms of convolved kk-th order Fibonacci numbers and the formula of E(Γn(k))|E(\Gamma^{(k)}_{n})| of linear expression of kk consecutive kk-th order Fibonacci numbers.

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Cite

@article{arxiv.2601.17273,
  title  = {The size of $k$-th order generalized Fibonacci cubes},
  author = {Jianxin Wei and Yujun Yang},
  journal= {arXiv preprint arXiv:2601.17273},
  year   = {2026}
}