I am struggling to find such languages $L_1$, $L_2$, and $L_3$ such that $L_1\subset L_2\subset L_3$ where $L_1,L_3\notin$ RE and $L_2\in$ R.  I know they exist, I need help finding them.
I am struggling to find such languages $L_{1}$, $L_{2}$, and $L_{3}$ such that  $$ L_{1} \subseteq L_{2} \subseteq L_{3} $$ where $L_{1}, L_{3} \notin  \mathbb{R}$ and $L_{2} \in  \mathbb{R}$.  I know they exist, I need help finding them.
Why should I "watch" a nearby Pokémon? Denoting the end of example/remark What is the etiquette to denote the end of an example or remark? For proofs, it's the QED symbol (white box). I know it's not necessary for everyone, but I would like to use it to break up the text a little. What should I use? A circle or filled box or what? What is the definition and purpose of a pre-amplifier? I find in many places mentions of pre-amplifiers being used to boost audio signals prior to feeding to a power amplifier.  Wikipedia's article on  gives some hints at their usage, but it doesn't really explain why it would be necessary to have two amplifiers in series rather than a single one with greater gain.  If a pre-amp is just a power amp with a smaller gain, what's the point, and why the distinction between the two kinds? Is the distinction in function, or simply purpose? Coffeescript existential operator sometimes checks against undefined, but not always How to create an iso from current installation I installed Ubuntu 14.04.1 on one of my laptops and now I want distribute that exact installation to a few of my friends. I tried making an iso with Gparted on a live session but it makes a 500 GB file (I've only used around 8 GB) .   Thanks in Advance ! The abstract environment changes the \linewidth for the whole document In the article class, it seems that using the abstract environment has an effect to the rest of the document. More precisely, it seems that it redefines the \linewidth, which equals \textwidth without abstract, is smaller with the abstract. My feeling is that \linewidth is redefined for the abstract environment, but the value is not reseted at the end of the abstract.  Here is a minimal example:  \documentclass{article} \begin{document} \abstract{This is an abstract. This is an abstract.}\bigskip  This is text. This is text. This is text. This is text. This is text. This is text.\\  \rule{\textwidth}{3em} \rule{\linewidth}{3em} \end{document}   The output is not the same if you comment the \abstract line or not.  Do you have the same problem as I do when you compile (if not, I will upload some PDF files to show)? Is this a (known) bug in LaTeX2e? How can we circumvent the problem?  Note: I compile with the pdflatex command, and I use pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009/Debian). I am running Ubuntu GNOME 15.10 with GNOME 3.18, and I would like to know if I can do any of the following and if so how:   Make it so that a folder is not indexed but leave its contents indexable (so that if I search for that folder's name in my system nothing will come up, but if I search for its contents, that will come up) Make it so that a folder is not indexable and nor is any of its contents (and if it contains sub-folders within it then it should recursively not allow any contents in them to be indexed nor the contents of any sub-sub-folders in the sub-folders etc, nor any of those sub-folders themselves) Make it so that individual files in a folder are not indexable, though not having any impact on other contents nor the parent-folder   So, are any of these variants possible? I believe the indexing program is called Tracker which indexes files and folders and their contents and allows for one to search for them on the system. How can I send same email multiple times in iOS? I wanted to send a single email to different users. I save an email to drafts and send the email to a user and it goes to the sent box instead of staying in the drafts box. Is there a way I can send an email repeatedly from the drafts box? How do I create a new object using Python in Blender 2.80? As part of an existing add-on, I'm trying to create an object and add it to the scene using Python. I followed a Blender Cookbook tutorial found here: . I use the following code to do so:  emptyMesh = bpy.data.meshes.new('emptyMesh') theObj = bpy.data.objects.new("object_name", emptyMesh) bpy.context.scene.objects.link(theObj)   But I get the following error when I try to link theObj to the scene objects:  AttributeError: 'bpy_prop_collection' object has no attribute 'link'   This works just fine in Blender 2.76-2.79, but doesn't work in the 2.80 test build I downloaded. Was there a change to the Python API? Or is this maybe a bug in the test build? My son is 5 years old.   Over the last few months I have been observing some disturbing sexual behavior from my child.  He is rubbing his penis on  the bed or pillow. Sometimes he would get naked and rub very tightly and make some sounds of pleasure! Previously, I thought he was playing... but later I understood.   His father doesn't want me to scold him, but one day I was really surprised and shocked by one incident... when I was in deep sleep in the afternoon, I suddenly woke up and saw he had pulled up my skirt and trying to mount me! I was really shocked!  I'm really upset.  What should I do? After these instructions in the Python interpreter one gets a window with a plot:  from matplotlib.pyplot import * plot([1,2,3]) show() # other code   Unfortunately, I don't know how to continue to interactively explore the figure created by show() while the program does further calculations.  Is it possible at all? Sometimes calculations are long and it would help if they would proceed during examination of intermediate results. In the , the icon color for the various sites seems* incorrect: Whenever I select a main site, the icon is greyed out, and when ever I select the corresponding meta site, the icon is colored. My initial instinct was to think that the colors of the main/meta sites following the &quot;Switch sites:&quot; prompt should be switched. (Actually, it seems like it's just a UI thing. See the edit below.)  *Edit: Actually, the colors are technically not incorrect, since (as Jeremy Banks has pointed out) the icon shows &quot;the other&quot; site of the main/meta pair, and clicking on it is for switching to the respective other site. See the comment thread for some UI improvement ideas. I use the listings package for code listings and I turned the line numbers on. But they appear left of the paragraph. I want them inside the paragraph. In the documentation it looks just right. Here is my code:  \documentclass[12pt,a4paper]{scrartcl} \usepackage{listings} \lstset{numbers=left} \begin{document} \section{Test} Test \begin{lstlisting}     test() \end{lstlisting} \end{document} My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r.  Starting from rest, they both begin to accelerate towards each other. So we have the gravitational force between them as:  $$F_g ~=~ G\frac{Mm}{r^2}$$  How do we find out at what time they will collide?  What we're having trouble with is this function being a function of $r$, but I have suspected it as actually a function of $t$ due to the units of $G$ being $N(m/kg)^2$.  I've tried taking a number of integrals, which haven't really yielded anything useful.  Any guidance?  No, this is not an actual homework problem, we're just 2 math/physics/computer people who are very bored at work :) Does $\sum\limits_{n=1}^\infty\frac{1}{\sqrt{n}+\sqrt{n+1}}$ converge? Does the following series converge or diverge? $$ \sum\limits_{n=1}^\infty\frac{1}{\sqrt{n}+\sqrt{n+1}} $$ The methods I have at my disposal are geometric and harmonic series, comparison test, limit comparison test, and the ratio test. With constant travel, is it possible to not have a tax residence? How can I Remove .DS_Store files from a Git repository? How can I remove those annoying Mac OS X .DS_Store files from a Git repository? postfix doesn't work after iptables set up Benefit of date in URL segments I was curious about the date in URL segments, is there any SEO point of benefit? For example the following URLs:  http://techcrunch.com/2013/06/18/netflix-will-launch-in-the-netherlands-later-this-year-as-its-international-expansion-slows/ http://tips-for-new-bloggers.blogspot.in/2007/02/adding-favicon-icon-to-blogger-url.html  https://community.jivesoftware.com/blogs/jivespace/2013/05/15/eol-of-the-html5-ipad-web-app   In all the above URLs there is date segment. The information of those blogs can be fetched via blog stub like "netflix-will-launch-in-the-netherlands-later-this-year-as-its-international-expansion-slows" so why to use that date part? Gray iTunes album tracks I noticed that a few tracks from an album appear gray.    The tracks are downloaded, I can play them if I double click them explicitly, but they don't play as part of the album. If I click the album's "play" button, they're skipped (1 gets played, then 3, then 4, etc.)  Why is this happening and how can I prevent it?    I saw a similar question, , but that's not what I'm experiencing — for me, the songs do get downloaded and everything appears to be OK, they just get skipped when playing the album.