Convergence problem of $a_n=(1-\frac12)^{(\frac12-\frac13)^{...^{(\frac{1}{n}-\frac{1}{n+1})}}}$

OpenYear of origin: 2001

Posted online: 2021-07-11 01:00:10Z by Rafik Zeraoulia100

Cite as: P-210711.1

  • Dynamical Systems
  • Mathematical Physics
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Problem's Description

let us moving to telescopic sum using exponent ,Assume we have this sequence: $a_n=(1-\frac12)^{(\frac12-\frac13)^{...^{(\frac{1}{n}-\frac{1}{n+1})}}}$ with $n\geq1$ , This sequence can be written as power of sequences :${x_n} ^ {{{y_n}^{C_n}}^{......}} $ such that all them value are in $(0,1)$, We want to know if the titled sequence should converge to $1$ ?

Many attempts are given here in SE to show whether the titled limit exist or not ,heropup claimed that numeric calculation of the sequence $\{a_n\}_{n \ge 1}$ suggests that the terms are bounded, but alternate between approximately $$0.56778606544394002098000796382530333102219963214866$$ and $$0.85885772008416606762434379473241623070938618180813$$ but I do not have a proof. This convergence is extremely rapid, and the alternating nature suggests that it is important to look at even and odd $n$ separately.In the meanwhile Barry Cipra showed the limit of the titled sequence can't be $ 1$ . The titled sequences assigned the two following Zeraoulia sequencesA328941 and A328942 in OEIS according to the parity of both odd and even iteration. S Dolan stated the following theorem:


The limit $L$ for the zeraoulia rafik sequence satisfies $$0.8588< L< 0.8589.$$

One can conclude that the upper and lower bound probably coincide and would be equal yield to proof the existence of limit of the titled sequence. Now according to the given attempts we are ready to reformulate the problem of convergence regarding that sequence as :

Problem: What is the exact limit of $a_n=(1-\frac12)^{(\frac12-\frac13)^{...^{(\frac{1}{n}-\frac{1}{n+1})}}}$, $n\to \infty$ if it exists ?

  1. ArticleIs an originIterative Sequences for Asymptotically Quasi nonexpansive Mappings with Error Member

    Journal of Mathematical Analysis and Applications Volume 259 (Issue 1), Pages 18-24, 2001

  2. ArticleIs an originThe strange properties of the infinite power tower

    year of publication: 2019arXiv

  3. ChapterIs an originRecursive sequences, discrete dynamical systems and their limits

    year of publication: 2015

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  • Edited: (general update ) at 2021-07-13 17:41:51Z

  • Created at: 2021-07-11 01:00:10Z View this version