Can anyone help to find a formula for this?     $$\sum_{k=1}^n\frac{k}{(1+r)^k}=\frac{1}{1+r}+\frac{2}{(1+r)^2}+\frac{3}{(1+r)^3}+\cdots+\frac{n}{(1+r)^n}.$$   I cannot seem to use $\dfrac{n(n+1)}{2}$ in anyway.
I want to know the general formula for $\sum_{n=0}^{m}nr^n$ for some constant r and how it is derived.  For example, when r = 2, the formula is given by: $\sum_{n=0}^{m}n2^n = 2(m2^m - 2^m +1)$ according to   Thanks!
Can "whatever" be split into two words? I tend to write, "say whatever they want", but I'm always tempted to write "say what ever they want". Is it acceptable to split the word in this context? What are the requirements for a (beta) site logo? Find the product $\prod_{n=1}^{\infty} (1+x^{2n-1}) $ How to prove that total number of non-isomorphic labelled trees of order $n$ is $n^{n-2}$? I predicted the formula by finding total number of non-isomorphic labelled trees of order 1 is 1 , order 2 is 1,order 3 is 3,order 4 is 16,order 5 is 125.But how do i prove it ? I am beginner in graph theory so i will be very thankful if i get some simple approach to solve the problem(Not by using some difficult theorems). Are there guidelines on how much free RAM a phone should have - specifically Samsung Galaxy S? What are the left and right ideals of matrix ring? How about the two sided ideals? While using MathJax to typeset binomial coefficients, I came across this problem of different sized brackets if my lower index contains the '0' character. Is there anyway to make the brackets the same size? I've just installed MariaDb on a fresh Ubuntu Gnome and ran  afterwards where I set a decent admin password, removed the anonymous user etc.  Afterwards I realized some strange behavior regarding the admin password:   If I try to login from my normal user account using the command mysql -u root -p I always get an error: ERROR 1698 (28000): Access denied for user 'root'@'localhost' I'm pretty sure I entered the correct password which I set with  earlier... When I run the command from root using sudo mysql -u root -p, I always get access to the database, no matter which password I actually enter...   Is this normal behavior, am I doing anything wrong or have I somehow screwed up the installation? Can I still command/control concentration spells while in the Border Ethereal? If I have cast something like Animated Objects or Bigby's Hand and then follow up the next round with casting Etherealness, can I still command/control those spells? How do you sort a dictionary by value? I often have to sort a dictionary, consisting of keys &amp; values, by value. For example, I have a hash of words and respective frequencies, that I want to order by frequency.  There is a SortedList which is good for a single value (say frequency), that I want to map it back to the word.   orders by key, not value. Some resort to a , but is there a cleaner way? If you're not used to seeing the 'low on internal storage' notification, what is it that you're doing to keep your phone's internal memory from filling up so quickly?   The 'SD Card and Phone Storage' menu in the settings doesn't really tell me much other than how much is free. And, I don't really have that many applications installed. The top 5 storage hogging apps on my phone are Gmail (18.6 MB), Twitter (17.5 MB), Facebook (12.55 MB), Maps (9.63 MB), and Swype (6.06 MB).  So, are there apps out there (besides your normal file manager ones, like Astro) that will help monitor internal phone storage? Is there something I should be doing to keep my phone storage use to a minimum? I have defined my own language whose syntax is very close to the one of Pascal. I would like to type the following program for instance. Many people use the packages algorithmicx or algorithm2e to print programs, but it seems that we have to use their specific keywords of its syntax like procedure, end while.  I just want to indent spaces when needed, and bold some words when I want (sorry that I could not bold letters in the following figure). Do I have to use  texttt for each line? Also, with verbatim, I could not bold words...  Also, as the program is not large, I would need to put it on the left side of the page, and leave space for some explanasion text on its right hand side. So I  guss I need to get them all together, and use multicols.  Could anyone help?  program test                                      some text here var   i : integer;                                    ...    b : boolean; begin    i := 1;                                        ...    b := true;    while i &lt; 15 do       i := i  + 1;       b := not b                                  some text here    od end   Edit1: Following @Werner's tabbing solution, I have made the code a minipage:  \begin{minipage}[t]{0.48\linewidth}% \begin{tabbing} Werner's solution \end{tabbing} \end{minipage}\hfill \begin{minipage}[t]{0.48\linewidth} a paragraph \end{minipage}   Actually as the code shows, I want the texts to be another separated minipage on the right hand side of the code. I have then 2 questions:   is it reasonable to make 0.48\linewidth instead of 0.5\linewidth? 0.48\linewidth is a conventional choice? is it possible to make a frame around the code, and use \caption and \label to make it a reference (I prefer figures)? How can I use variables in the LHS and RHS of a sed substitution? I want to do:  cat update_via_sed.sh | sed 's/old_name/new_name/' &gt; new_update_via_sed.sh   in my program.  But I want to use variables, e.g.  old_run='old_name_952' new_run='old_name_953'   I have tried using them but the substitution doesn't happen (no error). I have tried:  cat update_via_sed.sh | sed 's/old_run/new_run/' cat update_via_sed.sh | sed 's/$old_run/$new_run/' cat update_via_sed.sh | sed 's/${old_run}/${new_run}/' gnome-software on Ubuntu 16.04 doesn't work Is changing your passport a good strategy for removing a negative immigration history in Schengen? When certain nationalities of people want to travel in the Schengen zone, they are required to apply for a Schengen visa. This is a straight-forward process for most, but when an applicant has had problems with removals or refusals they may be reluctant to apply because they want to avoid the complexities of serial visa refusals. This reluctance may lead some into wondering how their history can be expunged, and this line of thought inevitably leads to the idea of getting their passport replaced with a new one.  This sounds like a great formula for people who have had prior refusals or removals.  In essence they can become 'reincarnated' as a first-time traveller and hence avoid the unpleasantness of revealing their prior interactions with the Schengen authorities.  The relevant parts of the application form are shown here...    Nothing asks about a prior removal or refusal, and the applicant is left with simple denials for 3 questions in order to present themselves as a first-time traveller.  Assuming the person is happy to set aside the moral issues associated with denying their history, are there any holes to this strategy?  This question is scoped to Schengen visa applications so that it will not be unmanageably broad, but answers from other regimes (particularly the affluent Commonwealth and the USA) are acceptable as long as the main points are relatively consistent with Schengen. What is god for religious people? In order to discuss with religious friends about god, I would like to know if there's some accepted objective definitions of God for main religions, even if belief is subjective.   For example, is he "a person who..."? In that case I would address features of a person, as capabilities and limitations. Is he "an entity..."? In that case I would use systems theory.   I feel lost on this, being agnostic from a religious family, where I was taught that God is a mess of things, including a beautiful bearded face, omnipotence and a mix of human defects and metaphysical powers. Can't execute .out files, getting permission denied I have written a C++ program and complied it to produce a.out file. However, whenever I try to run it, I get Permission Denied. I read that we can use sudo, but I can't quite get it to work. I use something like, sudo "./a.out" but that too doesn't work.  Edit:  Here is the message I get when I try "./a.out".  bash: ./a.out: Permission denied How can I detect inside a TeX file which engine (pdftex/xetex/luatex) is used to compile the file? Is there a LaTeX package that provides this functionality? "At" vs. "in" before verb In a document I found the following sentence:     listeners are more accurate at understanding speech spoken in their own accent...   Would it be an error to use "in" instead of "at"?  Actually in this case "at" sounds better than "in", but in general before verb is "at" always used? I just can't seem to figure this one out.  I want to use the command line to connect to a MySQL database residing on another server.  I went ahead and created the username and password for the user.  I have also granted all privileges on that user for that database.  When using the command: mysql -h &lt;hostname&gt; -u &lt;username&gt; -p, I get the following error:  ERROR 1045 (28000): Access denied for user '&lt;username&gt;'@'&lt;local_machine_hostname&gt;' (using password: YES)   The problem is that it keeps appending the current machine's hostname into the username.  Obviously, that user@&lt;local_machine_hostname&gt; is not correct.  It doesn't matter what I type.  For instance, if I type:  mysql -h &lt;hostname&gt; -u '&lt;username&gt;'@'&lt;hostname&gt;' -p   It does the same, only in the error output, it says:  Access denied for user '&lt;username&gt;@&lt;hostname&gt;'@'&lt;local_machine_hostname&gt;'   Is there a setting in a configuration file which is allowing this to happen?  It's really quite annoying.  I need to set up a tikiwiki server, and it cannot connect because during the step where you set up mysql, it keeps appending the local machine's hostname to the mysql login name.