English

Zeckendorf family identities generalized

Combinatorics 2026-04-14 v3

Abstract

Philip Matchett Wood and Doron Zeilberger have constructed identities for the Fibonacci numbers fnf_n of the form 1fn=fn1f_n = f_n for all n1n \geq 1; 2fn=fn2+fn+12f_n = f_{n-2} + f_{n+1} for all n3n \geq 3; 3fn=fn2+fn+23f_n = f_{n-2} + f_{n+2} for all n3n \geq 3; 4fn=fn2+fn+fn+24f_n = f_{n-2} + f_{n} + f_{n+2} for all n3n \geq 3; ...; the general identity in this family has the form kfn=sSkfn+skf_n = \sum_{s \in S_k} f_{n+s} (for all sufficiently high nn), where SkS_k is a finite set of integers that depends only on kk and contains no two consecutive integers. These identities are generalized, replacing the left-hand side kfnkf_n by arbitrary sums of the form fn+a1+fn+a2++fn+apf_{n+a_1} + f_{n+a_2} + \cdots + f_{n+a_p} for arbitrary integers a1,a2,,apa_1, a_2, \ldots, a_p. The resulting theorem is proved using the connection between the Fibonacci numbers and the golden ratio.

Keywords

Cite

@article{arxiv.1103.4507,
  title  = {Zeckendorf family identities generalized},
  author = {Darij Grinberg},
  journal= {arXiv preprint arXiv:1103.4507},
  year   = {2026}
}

Comments

10 pages. A more detailed version can be found at http://www.cip.ifi.lmu.de/~grinberg/zeckendorfLONG.pdf or in the ancillary files of this preprint. v3 corrects a (non-fatal) miscalculation

R2 v1 2026-06-21T17:43:26.835Z