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Firstly, my $\LaTeX$, Mathematics and English knowledge is very limited. It is extremely difficult for me to ask this question. Now I am improving myself.I hope you understand me...

Look at this function: $$f(n) = \begin{cases} n/2 &\text{if } n \equiv 0 \pmod 2 \\ n+1 & \text{if } n\equiv 1 \pmod 2.\end{cases}$$

We know that for any positive number, there is a number $\text{“}k\text{''}$, which that $f^k(n)=1$

For function $f(n)$ go backward from number $1$.

Let step number is $k$ $$[2^{\sum_{z=1}^{k-1} m_z}-2^{\sum_{z=2}^{k-1} m_z}-2^{\sum_{z=3}^{k-1} m_z}-\cdots-1]\stackrel{k\to \infty}{\longleftarrow}\mathbf{\cdots} \stackrel{k=5}{\longleftarrow} \mathbf{[2^{m_4+m_3+m_2+m_1}-2^{m_4+m_3+m_2}-2^{m_4+m_3}-2^{m_4}-1]}\stackrel{k=4}{\longleftarrow} \mathbf{[{2^{m_1+m_3+m_2}-2^{m_2+m_3}-2^{m_3}-1}]}\stackrel{k=3}{\longleftarrow} \mathbf{[{2^{m_1+m_2}-2^{m_2}-1}]}\stackrel{k=2}{\longleftarrow} \mathbf{[{2^{m_1}-1}]}\stackrel{k=1}{\longleftarrow} \mathbf1$$

Then, $2^{\sum_{z=1}^{k-1} m_z}-2^{\sum_{z=2}^{k-1} m_z}-2^{\sum_{z=3}^{k-1} m_z}-\cdots-1=F_{10}(m_1,m_2,\ldots,m_{k-1})$ and $2^{\sum_{z=1}^{k-i} m_z}-2^{\sum_{z=2}^{k-i} m_z}-2^{\sum_{z=3}^{k-i} m_z}-\cdots-1 =F_{ij}(m_1,m_2,\ldots,m_{k-i})$

Let, for $\max [F_{10}]$ , we can write

$m_1=m_2=m_3=\cdots=m_{k-1}=p \Rightarrow \max[F_{10}]=2^{p(k-1)}-2^{p(k-2)}-2^{p(k-3)}-\cdots-1$ and for each $F_{ij}$ must be $\max [F_{ij}]<\max [F_{10}]$.

Then, Let's write all possible sums:

$$\sum_{m_{k-1}=1}^p \sum_{m_{k-2}=1}^p\cdots\sum_{m_{1}=1}^p F_{10}(m_1,m_2,\ldots,m_{k-1})+\sum \sum\cdots\sum F_{11}(m_1,m_2,\ldots,m_{k-1})+\sum\sum\cdots\sum F_{12}(m_1,m_2,\ldots,m_{k-1})+\sum\sum\cdots\sum F_{13}(m_1,m_2,\ldots,m_{k-1})+\cdots+\sum\sum\cdots\sum F_{20}(m_1,m_2,\ldots,m_{k-2})+\sum\sum\cdots\sum F_{21}(m_1,m_2,\ldots,m_{k-2})+\sum\sum\cdots\sum F_{22}(m_1,m_2,\ldots,m_{k-2})+\sum\sum\cdots\sum F_{23}(m_1,m_2,\ldots,m_{k-2})+\cdots+\sum\sum\cdots\sum F_{30}(m_1,m_2,\ldots,m_{k-3})+\sum\sum\cdots\sum F_{31}(m_1,m_2,\ldots,m_{k-3})+\sum\sum\cdots\sum F_{32}(m_1,m_2,\ldots,m_{k-3}) +\sum\sum\cdots\sum F_{33}(m_1,m_2,\ldots,m_{k-3}) + \dots + \cdots + \sum_{m_1=1}^{[log_2{(2^{p(k-1)}-2^{p(k-2)}-2^{p(k-3)}-\cdots-1+1)}]} (2^{m_1}-1) = M$$

What is $\sum\sum\cdots\sum F_{ij}(m_1,m_2,\ldots,m_{k-i})$ ?

Example: Let,$\sum\sum\cdots\sum F_{11}(m_1,m_2,\ldots,m_{k-1}) = \sum_{m_1=1}^1 \sum_{m_2=1}^1 \cdots \sum_{m_{k-2}=1}^1 \sum_{m_{k-1}=p+1}^{p+1}F_{11}(m_1,m_2,\ldots,m_{k-1})$

which that, $\max [F_{10}]>\max [F_{11}]$

İf $k\to \infty$ and $p\to \infty$ I think $\text{“}M\text{''}$ must be sum of all odd numbers, which that the last number equal to $2^{p(k-1)}-2^{p(k-2)}-2^{p(k-3)}-\cdots-1.$

The Question: Is this limit equal to $1$ ?

$$\lim_{k \to \infty}\left[ \lim_{p \to \infty} \frac{M}{1+3+5+7+\cdots+ [2^{p(k-1)} - 2^{p(k-2)}-2^{p(k-3)}-\cdots-1]}\right]=1$$

Zaharyas
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    you can easily arrive at $\lim \limits_{p \to \infty} \lim \limits_{k \to \infty} \frac{4 \left(2^p-1\right)^2}{\left(2^{k p}-2^{(k-1) p+1}+2^p\right)^2} M$, thus $M$ should behave like $\frac{\left(2^{k p}-2^{(k-1) p+1}+2^p\right)^2}{4 \left(2^p-1\right)^2} + \epsilon(p,k)$, so its up to you so see if this hold, or to upload a view-able picture. – Ahmad Sep 02 '17 at 15:23
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    To the downvoters: I know that the question is poorly worded, likely incomplete, and the image is hard to read (though it is readable if you open it outside the browser). That said, it's obviously not homework, but looks like a question the OP had in mind that they couldn't find an answer to, or even articulate completely. Maybe the question is only a few steps away from becoming intelligible and meaningful, and maybe MSE could help with covering those steps, rather than shoot it down. Just my opinion of course, but I believe anyone's curiosity in math should be encouraged, not dismissed. – dxiv Sep 03 '17 at 20:18
  • @Zaharyas Could you please explain what is meant by "For function $f(n)$ go backward from number $1$?" Additionally, right after that, what's your method of computing those "steps"? – Andrew Tawfeek Sep 04 '17 at 20:11
  • @AndrewTawfeek $A_2=A_1×2^n-1$ – Zaharyas Sep 04 '17 at 20:23
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    So.... $M=31$, simply? For fixed $M$ and $k$, the inner limit is clearly $0$. With that, $\lim_{k\to\infty} 0 = 0$. – Hagen von Eitzen Sep 04 '17 at 21:31
  • This is only example. How to calculate $M$. – Zaharyas Sep 04 '17 at 21:38
  • The problem really isn't the LaTeX, it is the definition of what you want. What do you mean by "For function $f(n)$ go backwards from $1$?" Also, "Let step number is $k$ (followed by some terrible expression that means nothing.)" What are you trying to say. – Thomas Andrews Sep 04 '17 at 22:16
  • @Thomas Andrews I fixed..$f^k(n)=1$ – Zaharyas Sep 04 '17 at 22:51
  • For $2^{m_1}-1$, $\frac{2^{m_1}-1+1}{2^{m_1}}=1$ and $k=1$ – Zaharyas Sep 04 '17 at 22:53
  • Why did you tag me - that didn't address either of my complaints. – Thomas Andrews Sep 04 '17 at 23:42
  • My opinion is that you may really want to clarify what your diagram means. In particular, how are your numbers $m_1, m_2,\cdots$ defined and what does the notation $[ \square ]\stackrel{k=\square}{\leftarrow}$ refers to? I guess I am not the only one who is stumbling at this step. – Sangchul Lee Sep 04 '17 at 23:42
  • You won't get far without clarifying your notation. It looks like noise. Why is some stuff bold and other stuff not? What are you doing when you suddenly write invented notation for "step $k$?" Help people help you. You seem to assume people can read your mind. We cannot. – Thomas Andrews Sep 04 '17 at 23:48
  • $A_2=A_1×2^n-1$ =>$(2^{m_1}-1)×2^{m_2}-1$ ... – Zaharyas Sep 05 '17 at 04:09
  • $(2^{m_1+m_2}-2^{m_2}-1)×2^{m_3}-1$ and $k=3$ because after $3$ steps $f(n)=1$ – Zaharyas Sep 05 '17 at 05:27

2 Answers2

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(too long for a comment, too)

Although I deeply understand the pain of writing in a second language, you can still try to make every idiosyncratic notation or terminology clear to everyone. It is still very difficult to follow, due to lots of notations which are left unexplained.

Let me give an example by refining part of your question which I think that I am following.


Consider the function $f:\mathbb{N} \to \mathbb{N}$ on the set of positive integers $\mathbb{N} = \{1,2,\cdots\}$ defined by

$$ f(n) = \begin{cases} n/2 & \text{if $n$ is even} \\ n+1 & \text{if $n$ is odd} \end{cases} $$

We know that for each $n\in\mathbb{N}$, there exists $k\geq1$ such that $f^{k}(n)=1$ where $f^k$ is the $k$-fold composition of $f$.

Now we would like to track this dynamics backward. This may be formally described by considering sequences of the form $\mathbf{a}=(1=a_0,a_1,a_2,\cdots)$ that satisfy $a_i=f(a_{i+1})$ for all $i$. We focus on the indices $i$ that satisfy $a_{i-1}=a_{i}+1$. Enumerating all such indices in increasing order, we obtain a sequence $(i_k)$. (Here, we suppress the dependence on $\mathbf{a}$ from notation for brevity.) We call $i_k$ the $k$-th step of $\mathbf{a}$. Then the locations of steps are determined by specifying the gaps $m_k = i_k - i_{k-1} - 1$ for $k \geq 1$, where we adopt the convention that $i_0 = 0$. Then

\begin{align*} &a_{i_0} = 1\\ \xrightarrow{\text{next step}} \quad& a_{i_1} = 2^{m_1} - 1 \\ \xrightarrow{\text{next step}} \quad& a_{i_2} = 2^{m_1+m_2} - 2^{m_2} - 1 \\ \xrightarrow{\text{next step}} \quad& a_{i_3} = 2^{m_1+m_2+m_3} - 2^{m_2+m_3} - 2^{m_3} - 1 \\ \xrightarrow{\text{next step}} \quad& \cdots \end{align*}


And for the rest of your question, especially regarding quantities $F_{ij}$, I have no idea what you are trying to say. At least I can understand is that (borrowing some of my notations)

\begin{align*} F_{1,0} = F_{1,0}(m_1, \cdots, m_k) &= [\text{$a_{i_k}$ with the first $k$ gaps given by $(m_1, \cdots, m_k)$}] \\ &= 2^{m_1+\cdots+m_k} - \left( \sum_{l=2}^{k} 2^{m_l+\cdots+m_k} \right) - 1 \end{align*}

and that

$$ \max\{ F_{1,0} : m_1, \cdots, m_k \in \{0,\cdots, p\} \} = F_{1,0}(\underbrace{p, \cdots, p}_{\text{$k$-tuple}}). $$

Sangchul Lee
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  • Perfect..you ar correct..You understand me.. – Zaharyas Sep 05 '17 at 08:00
  • I wrote an example..Please can you look?? – Zaharyas Sep 05 '17 at 14:18
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    @Zaharyas, It still looks like a riddle to me. You are still not telling us what is $M$. Although it may be hard to describe it mathematically, certainly you would have an idea of how your quantity should be formed. For example, instead of writing $$C=\sum_{j=1}^{k}\sum_{\substack{m_1,\cdots,m_j\0<F_{10}(m_1,\cdots,m_j)<F_{10}(p,\cdots,p)}} F_{10}(m_1,\cdots,m_j)$$ you can describe $C$ verbally as the sum of all numbers which can be obtained by applying operations $n\mapsto2n$ and at most $k$ operations $n\mapsto(n-1)$ to $1$ and do not exceed $F_{1,0}(p, \cdots \text{($k$-tuples)}, p)$. – Sangchul Lee Sep 05 '17 at 17:23
  • Yes, you are correct!!! – Zaharyas Sep 05 '17 at 18:06
  • Now is the question clear? – Zaharyas Sep 05 '17 at 18:24
  • Can you edit my question?? I can not this.. – Zaharyas Sep 05 '17 at 18:54
  • What do you think about this question??ıs this stupid question?? – Zaharyas Sep 05 '17 at 21:29
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    @Zaharyas, Well, I think your question has potential to attract people if properly stated. But our communication seems failing now. This is your question, so it is your duty to convince people to spare their time to get into it. But I still don't understand what you are trying to say. Honestly I don't want to spend my time on deciphering your unexplained notations. If it is hard to describe them in words, why don't you provide concrete examples or even drawings? You may probably be able to visualize $M$ using Collatz graph. – Sangchul Lee Sep 06 '17 at 03:14
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(Too long for a comment.) The question is difficult to follow, even with the additional details in the posted image. To me, it looks like it might have something to do with the "total stopping time" of the Collatz-like function $g(n)$, only defined as $n+1$ in the odd case, instead of $3n+1$. If my guess is wrong, please stop reading and post a comment so that I remove this post. Even if you keep reading, note that it is not an answer, just some related thoughts which may or may be not useful.

The modified $g(n)$ is known to always go to $1$ if repeatedly iterated, see this answer for example.

About how "fast" it goes to $1\,$, let $\gamma(n)=l$ be the lowest positive integer such that $g^{\,l}(n)=1\,$. Some bounds on $\gamma(n)$ can be derived by looking at some particular cases.

The "fastest" descent to $1$ happens when the iterations consist of divisions, only. This means all intermediate values are even, which happens iff $n=2^k\,$, and in that case $g^{\,k}(n)=1$ so $\gamma(2^k) = k$.

The "slowest" descent to $1$ happens when iterations alternate between additions and divisions. This means $n=2^k+1\,$, and in that case $g^{\,2k}(n)=1$ so $\gamma(2^k+1)=2k\,$.

Of course, $\gamma(n)$ is not monotonical in $n$, so the above do not give "hard" bounds for arbitrary $n\,$, but it still follows that $\;\displaystyle \liminf_{n \to \infty} \frac{\gamma(n)}{\log_2(n)} \le 1\;$ and $\;\displaystyle \limsup_{n \to \infty} \frac{\gamma(n)}{\log_2(n)} \ge 2\,$.

dxiv
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  • Yes, you are right $g(n)$ is Collatz like function. – Zaharyas Sep 03 '17 at 21:02
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    +1) I am grateful for your support!I made a final decision. I will write the whole question in Latex. Unfortunately, I could not express the question well. I will make the question understandable .It will take more hours.. Because I use the android keyboard.and my latex knowledge limited. You inspired me. – Zaharyas Sep 03 '17 at 22:51