Why is there nothing good coming from the East?
Is Tolkien prejudiced against the East?
Squares in arithmetic progression It is easy to find 3 squares (of integers) in arithmetic progression. For example, $1^2,5^2,7^2$.  I've been told Fermat proved that there are no progressions of length 4 in the squares. Do you know of a proof of this result?   (Additionally, are there similar results for cubes, 4th powers, etc? If so, what would be a good reference for this type of material?)    Edit, March 30, 2012: The following  in MO is related and may be useful to people interested in the question I posted here. How can I copy the contents of a folder to another folder in a different directory using terminal? I am trying to copy the contents of a folder to another folder in a different directory using terminal.  Would somebody be able to provide me an example of the command line syntax required to achieve this? When Bottom Navigation Isn't Best I'm developing a mobile app and dealing with various UI/UX issues. I'm open to all kinds of ideas at this stage, however some designers I consult with seem to be zealots for bottom-navigation and are hesitant in actually analyzing whether the bottom-nav is actually best for my app; they just want me to use the bottom tabs navigation as if it's some UI law.  One point I try to bring up is that my business model has users who aren't typical one-handed mobile users, are tech savvy, would use my app more of a tool, and would spend only a few minutes in it. The app isn't a typical lazy-content-browsing experience where you want to minimize fingers-over-top-of-screen interference, and where you want to keep the use transfixed and spending time in the app.  Anyways, I'd like to hear about situations where a bottom nav was decided-on, or started-with, and you had good reason to eliminate it and go with another navigation design.  Most articles out there talk about eliminating hamburger menus and diving into bottom nav. Is the converse simply going back to hamburger menu? How can I reduce the delay before window previews are shown in the Windows 7 taskbar? I really love the preview feature of the Windows 7 taskbar. There's only one reason I don't use it more often -- it takes a relatively long time to display the actual window.  There is a registry trick () to reduce the delay used by general menus, and make the submenus open instantly when hovered upon. I'm wondering if there's a similar trick that can be used for the Windows 7 taskbar's previewing. Will I need any Malaysian Rinngit at Kuala Lumpur airport when I'm leaving the country? First Bash Script Problem Where does the phrase "on the lam" come from? According to the Online Etymological Dictionary, lam means:     "flight," as in on the lam, 1897, from a U.S. slang verb meaning "to run off" (1886), of uncertain origin, perhaps somehow from the first element of lambaste, which was used in British student slang for "beat" since 1590s.    Does anyone know of any other explanations? $a+1,a-1$ invertible for nilpotent element Given a ring $R$ (with unity), prove that if $a \in R$ is nilpotent, then $a+1,a-1$ are both invertible.   Suppose $a^n=0$. Then $1=1-a^n=(1-a)(1+a+\ldots+a^{n-1})$, so $1-a$ is invertible.  If $n$ is odd we can use $1+a^n=(1+a)(1-a+\ldots+a^{n-1})$.  But what if $n$ is even? At least it's my understanding that AES isn't affected by known-plaintext. Is it immune to such an attack, or just resistant? Does this vary for chosen-plaintext? Does Python have a ternary conditional operator? If Python does not have a ternary conditional operator, is it possible to simulate one using other language constructs? How to partition harddisk for Ubuntu 18.04 I want to partition my hard disk, but I don't have any other software running(like dual booted).  And I do not know how to do it. Can you send the instructions? How to calculate the prediction interval for an OLS multiple regression? What is the algebraic notation to calculate the prediction interval for multiple regression?  It sounds silly, but I am having trouble finding a clear algebraic notation of this. Making Map Book of pages with same area shown but different layers turned on/off In ArcMap a Map Book is best suited for a series of features that each get their own page. It allows you to pick a feature and generate a Map Book Page for each feature including any additional information you wish to add to each page via dynamic text, charts, etc. Is there an alternative for say a series of pages showing the EXACT same area but with different layers turned on and off? We have a Capital Improvements document that I have to create showing the City Boundaries on every page. One page has all police and fire stations listed, another shows proposed water systems, another shows expressways and highways and work being done near or on them... etc., ad nauseum. Is there some way to set this up so that I DON'T have to created a separate MXD for each Map Page of this document? Changing the keyboard layout turns off the numlock This questions has been asked before too and I did go through most of the suggestions. Things I have tried so far: setting up correct  path variable environment, installing anaconda 32 bits, python 2.7, or even switching to python 2.7 in cmd while initially using Anaconda 3 , adding Desktop 10.4.pth file with  following path.  C:\Program Files (x86)\ArcGIS\Desktop10.4\bin C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcToolBox\Scripts   I also added those paths in environment variable   These suggestions help me to reduce the error. But Now I am getting a different error. Looks like python can find arcpy but missing another package.  Getting this error while trying to import arcpy in python 3.6.   File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\__init__.py", line 22, in &lt;module&gt;     from arcpy.geoprocessing import gp    File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\geoprocessing\__init__.py", line 14, in &lt;module&gt;     from _base import *  ModuleNotFoundError: No module named '_base'   Any suggestions? FFMPEG video from images comes out same (yet incorrect) duration regardless of frame rate How do I disable the resizable property of a textarea? When should a Test Case be marked as "No Apply"? Odd behavor with POSIXct/POSIXlt and subsecond accuracy adding a point in a manipulate command