I am getting null pointer exception below
What is a NullPointerException, and how do I fix it?
I recall from complex analysis a while ago that the series $$\sum_{n=1}^\infty \frac{z^{n!}}{n}$$ has radius of convergence 1, diverges on roots of unity, and converges elsewhere on the circle. It's simple enough to see that it has to diverge on roots of unity: consider $z$ such that $z^k = 1$ for some $k \in \mathbb{N}.$ Plug this into the series and you see that past the $k$'th term, $z^{n!} = (z^k)^m = 1$ for some $m \in \mathbb{N}$; hence, the series becomes harmonic and must diverge.  But I don't recall how to show that the series converges for other values on the circle. If this is simple I'd like just a hint, if it is involved I would prefer a sparse outline of the proof. Thank you! I am trying to rename my Windows / Boot Camp partition from "EFI Boot" to "Boot Camp" or "Windows". But I do not figure out where to rename.   I tried bless command on the NTFS Volume, I tried creating the folders "System/Library/CoreServices" and copied the .disklabel file into it (or also blessit) but nothing changed.  Finally I got the Volume Icon on Boot Selection to work by copying the icns File onto the EFI partition. Also tried blesson the EFI partition – but this also do not work.  So I have my Icon, but I also would like to rename it – how can I do this?  Systems are Windows 10 and macOS Mojave. I have recently installed ubuntu 11.10. But when i try to install a software it tries to 'updating cache' but after a while, it stops, showing:                            Failed to download repository information                           Check your internet connection   so, now i am totally unable to install any software in my ubuntu.  Please,let me know how to solve the problem. Do we have different set of badges in different SE sites. eg. I don't see any 'Pundit' badge in badges popup in Hinduism SE.  Also, if the above is true, then can we include the left badges in a SE site at a later stage. How can we communicate short messages long-distance? In our 5e game, we stole a boat. And a horse carriage. And a lot of other stuff for moving things between cities.   Our DM meant for this to be a way to skip road encounters. We decided to fund a shipping company and hire managers (Knights retainers, etc.) to turn a profit. The DM ruled that these would cover lifestyle expenses, provide us with easy smuggling, etc.   However, we want to keep tabs on the treasure we're moving back and forth.   What can we use for communicating with our managers from anywhere in the world? What about from say, across the city?  We don't need to communicate often or for long - a single round will work. All we need is for the manager to say "we need you back" Why teach linear algebra before abstract algebra? Is there a reason why most undergraduate curriculums put linear algebra before abstract algebra?  I'm asking this because personally it seems to be much easier to understand the architecture behind linear algebra as supposed to simply solving problems after a course in abstract algebra. Why is "our today's meeting" wrong? One of the answers to  question states that &quot;We shall discuss it in our today's meeting&quot;  is grammatically correct. To me, that sentence is clearly wrong. While in today's meeting is fine and in our today meeting is OKish (though at the very least clumsy), there's something about the possessive there (our today's) that makes it wrong for me. I would read that sentence as in our today's (as opposed to your today's) meeting. Similar to in our car's trunk where the our clearly modifies car and not trunk or car trunk, the our in our today's seems to be modifying today's and not meeting. So, my questions are i) is it actually grammatically wrong to say in our today's or is it just a question of usage? and ii) if it is indeed wrong, how can we explain its wrongness? File permissions and saving How to get Scilab 6.0.1 working on Ubuntu 18.04 LTS? I have installed clean Ubuntu MATE 18.04 LTS and installed Scilab from repository here with    sudo apt-get update sudo apt-get install scilab   After installation I tried to launch it from GUI (Applications → Other → Scilab) - it does not start. Then I tried to launch it from terminal with scilab command. Terminal output is as follows:  $ scilab /usr/bin/scilab-bin: error while loading shared libraries: libjava.so: cannot open shared object file: No such file or directory   so it can't find Java. I reported  about this problem.  I checked existence of libjava.so:  $ dpkg -S libjava.so   openjdk-11-jre-headless:amd64: /usr/lib/jvm/java-11-openjdk-amd64/lib/libjava.so   so it is in place.  What should I do to get Scilab 6.0.1 working on Ubuntu 18.04 LTS? Why would one suppress the intercept in linear regression? In a number of statistical packages including SAS, SPSS and maybe more, there is an option to "suppress the intercept". Why would you want to do that? I've done a clean install of 18.04 and I can't open desktop folders, not even the desktop trash can. Anybody else had this issue? I click on the desktop folders (double click) and nothing happens.  Strange enough, I can open  them when using Nautilus and going to home\stackinator\desktop\ or whatever the path is (can't remember at this point). Limit of Multivariate Probability Density Function as one or more or all variables approach positive or negative infinity Could someone point out a good source or provide justification as to whether the limit of a multivariate probability density function, as one or more or all variables tends to positive or negative infinity, goes to zero.  $$\lim_{x_{1}\to\pm\infty}f(x_{1},x_{2},...,x_{n})=0$$  $$\lim_{x_{1},x_{2}\to\pm\infty}f(x_{1},x_{2},...,x_{n})=0$$  $$\lim_{x_{1},x_{2},...,x_{n}\to\pm\infty}f(x_{1},x_{2},...,x_{n})=0$$  I have found this related question for the univariate case: In a linear program, I have a variable $y$ that must obey $y=\max(x-a,0)$ where $x$ is a linear combination of the other variables and $a$ is a constant. $x$ and $y$ and $a$ are always non-negative. If the objective function decreases w.r.t. $y$, then adding the constraint $y\geq x-a$ makes it work. Are there any way to add dummy varibles and contraints such that $y=\max(x-a,0)$ when the objective function increases w.r.t. $y$? I can't say $y\leq x-a$ because if $x-a&lt;0$ it contradicts the non-negativity of $y$ whereby the solution might no longer be in the feasible region or the problem might even be infeasible. Vertical alignment of align* in enumerate Related (but not the same):         Earlier today I asked a question about aligning equations in an enumerate environment and got an answer that seemed to work for the example I gave, but it turns out I wasn't really specific enough for my problem.  I'm using align* environments, often as the only part of a list item. (If you're wondering why I'm not using more words to introduce the align*, these are mostly homework solutions where most of the work is algebra, etc.)  Here's my code and what it makes (above the middle line):  \begin{enumerate}   \item \begin{align*}     x^2 + y^2 &amp;= x^2 + (iy)^2 \\               &amp;= (x + iy) (x - iy)   \end{align*}   \item \begin{align*}     \frac{1}{n^2-4} &amp;= \frac14 \frac{4}{(n-2)(n+2)} \\                     &amp;= \frac14 \left( \frac{1}{n-2}-\frac{1}{n+2} \right)   \end{align*} \end{enumerate}     I'm trying to make the baseline of the first line of the align* environment the same as the number's baseline—I want the first line of the align* to have the same vertical position (centered horizontally in the same way) relative to its number as in the second half of my picture. (Side question: why is there so much space before the align* starts?) I sold an investment in a standard brokerage account at a small loss because I needed the money for a down payment.  I still think it is a good investment, can I buy the same investment in a standard IRA without running into wash sale problems?  I will probably just wait the 30 days any way to avoid any headaches, but I want to know if there is a definitive answer on this.    Being as the cost basis in the traditional IRA doesn't matter, I wouldn't think there would be a problem. Reload the page on hitting back button Why don't players get extra xp for large encounters? Based on the table Encounter XP Multipliers from the Basic Rules' DM section, Page 57, when you're building encounters in 5E, you include an XP modifier depending on the number of creatures your PCs will be fighting: 1.5x for a pair, 2x for 3-6 and so on. However, the PCs only get the base XP as a reward.     This doesn't change the actual xp reward ... just your calculations of how difficult the encounter is.   Why is this? After acknowledging that battles vs multiple opponents are more difficult, why not reward them as such? How to download an MP3 track from a YouTube video This is similar to , but I believe it's a bit different*.  Sites like GMail support a preference that pushes all traffic through the SSL edition of the site rather than the plain-text protocol.   For sites that don't offer such preferences (or ones that may, but I have been unable to find, like facebook), is there a way using only the browser (perhaps with a plugin or addon) to always try SSL first, and fall-back to plain-text iff SSL fails?  Is that solution available on Windows, Mac OS X, and Linux? Just one?     * The previous question was looking for external applications that would accomplish this goal. How to prevent the paragraphs to spread out over the page? I have a problem. I have several large equations within the text. And when LaTeX does not manage to put the equation on the same page and moves it to the next one, he spreads the paragraphs of the text in the first page. How could I prevent this? I know about \pagebreak and \newpage, but I do not want to force the \newpage, as the text may move (if I add something later or so on) and the pagebreaks may not be valid. I would like to make LaTeX not to spread the paragraphs over a page automatically. Is it possible?  I tried to make an example:  \documentclass[a4paper,12pt,twoside]{book} \usepackage{amsmath} \begin{document}  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&amp;+&amp;123 \\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ \end{eqnarray}  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&amp;+&amp;123 \\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ 123&amp;+&amp;123 \nonumber\\\ \end{eqnarray}  \end{document}