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Vestnik KRAUNC. Fiziko-Matematicheskie Nauki, 2025, Volume 52, Number 3, Pages 7–23
DOI: https://doi.org/10.26117/2079-6641-2025-52-3-7-23
(Mi vkam694)
 

MATHEMATICS

Generalized natural density $DF(\mathfrak{F}_k)$ of Fibonacci word

D. Abdullah, J. Hamoud

Moscow Institute of Physics and Technology
References:
Abstract: This paper explores profound generalizations of the Fibonacci sequence, delving into random Fibonacci sequences, k-Fibonacci words, and their combinatorial properties. We established that the nth root of the absolute value of terms in a random Fibonacci sequence converges to $1.13198824\ldots$, with subsequent refinements by Rittaud yielding a limit of approximately $1.20556943$ for the expected value's n-th root. Novel definitions, such as the natural density of sets of positive integers and the limiting density of Fibonacci sequences modulo powers of primes, provide a robust framework for our analysis. We introduce the concept of k-Fibonacci words, extending classical Fibonacci words to higher dimensions, and investigate their patterns alongside sequences like the Thue-Morse and Sturmian words. Our main results include a unique representation theorem for real numbers using Fibonacci numbers, a symmetry identity for sums involving Fibonacci words, $\sum_{k=1}^{b} \dfrac{(-1)^k F_a}{F_k F_{k+a}}= \sum_{k=1}^{a} \dfrac{(-1)^k F_b}{F_k F_{k+b}}$, and an infinite series identity linking Fibonacci terms to the golden ratio. These findings underscore the intricate interplay between number theory and combinatorics, illuminating the rich structure of Fibonacci-related sequences.
Keywords: density, Fibonacci, word, natural, sequence, balanced.
Received: 30.09.2025
Revised: 10.11.2025
Accepted: 11.10.2025
Bibliographic databases:
Document Type: Article
UDC: 517
MSC: Primary 68R15; Secondary 05C42, 11B05, 11R45, 11B39
Language: English
Citation: D. Abdullah, J. Hamoud, “Generalized natural density $DF(\mathfrak{F}_k)$ of Fibonacci word”, Vestnik KRAUNC. Fiz.-Mat. Nauki, 52:3 (2025), 7–23
Citation in format AMSBIB
\Bibitem{AbdHam25}
\by D.~Abdullah, J.~Hamoud
\paper Generalized natural density $DF(\mathfrak{F}_k)$ of Fibonacci word
\jour Vestnik KRAUNC. Fiz.-Mat. Nauki
\yr 2025
\vol 52
\issue 3
\pages 7--23
\mathnet{http://mi.mathnet.ru/vkam694}
\crossref{https://doi.org/10.26117/2079-6641-2025-52-3-7-23}
\edn{https://elibrary.ru/KCDDRW}
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