English

A new combinatorial interpretation of the Fibonacci numbers squared

Combinatorics 2019-11-05 v1

Abstract

We consider the tiling of an nn-board (a 1×n1\times n array of square cells of unit width) with half-squares (12×1\frac12\times1 tiles) and (12,12)(\frac12,\frac12)-fence tiles. A (12,12)(\frac12,\frac12)-fence tile is composed of two half-squares separated by a gap of width 12\frac12. We show that the number of ways to tile an nn-board using these types of tiles equals Fn+12F_{n+1}^2 where FnF_n is the nnth Fibonacci number. We use these tilings to devise combinatorial proofs of identities relating the Fibonacci numbers squared to one another and to other number sequences. Some of these identities appear to be new.

Keywords

Cite

@article{arxiv.1907.06517,
  title  = {A new combinatorial interpretation of the Fibonacci numbers squared},
  author = {Kenneth Edwards and Michael A. Allen},
  journal= {arXiv preprint arXiv:1907.06517},
  year   = {2019}
}

Comments

6 pages, 1 figure, to appear in Fibonacci Quarterly volume 57 issue 5 (2019)