On Higher Dimensional Fibonacci Numbers, Chebyshev Polynomials and Sequences of Vector Convergents

TL;DR

This paper explores higher-dimensional Fibonacci sequences generated through Chebyshev functions and recurrence relations, revealing their algebraic, combinatorial, and analytical properties, including convergence to algebraic points and connections to orthogonal polynomials.

Contribution

It introduces new higher-dimensional Fibonacci sequences with explicit constructions, recurrence relations, and links to algebraic numbers and orthogonal polynomials, expanding classical Fibonacci theory.

Findings

Sequences converge to irrational algebraic points in m

Sequences expressible via trigonometric sums and binomial polynomials

Orthogonal polynomials satisfy functional equations with zeros on the critical line

Abstract

We study higher-dimensional interlacing Fibonacci sequences, generated via both Chebyshev type functions and $m$-dimensional recurrence relations. For each integer $m$, there exist both rational and integer versions of these sequences, where the underlying prime congruence structures of the rational sequence denominators enables the integer sequence to be recovered. From either the rational or the integer sequences we construct sequences of vectors in $\mathbb{Q}^m$, which converge to irrational algebraic points in $\mathbb{R}^m$. The rational sequence terms can be expressed as simple recurrences, trigonometric sums, binomial polynomials, sums of squares, and as sums over ratios of powers of the signed diagonals of the regular unit $n$-gon. These sequences also exhibit a "rainbow type" quality, and correspond to the Fleck numbers at negative indices, leading to some combinatorial identities involving binomial coefficients. It is shown that the families of orthogonal generating polynomials defining the recurrence relations employed, are divisible by the minimal polynomials of certain algebraic numbers, and the three-term recurrences and differential equations for these polynomials are derived. Further results relating to the Christoffel-Darboux formula, Rodrigues' formula and raising and lowering operators are also discussed. Moreover, it is shown that the Mellin transforms of these polynomials satisfy a functional equation of the form $p_n(s)=\pm p_n(1-s)$, and have zeros only on the critical line Re $s=1/2$.