Why do different ISO images have different file sizes?
Why is the amount of photos that fit on one card dependent on ISO?
Proving $1-\exp(-4x^2/ \pi) \ge \text{erf}(x)^2$ As I have heard people did not trust Euler when he first discovered the formula (solution of the ) $$\zeta(2)=\sum_{k=1}^\infty \frac{1}{k^2}=\frac{\pi^2}{6}.$$ However, Euler was Euler and he gave other proofs.   I believe many of you know some nice proofs of this, can you please share it with us? How to convert strings into integers in Python? I have a tuple of tuples from a MySQL query like this:  T1 = (('13', '17', '18', '21', '32'),       ('07', '11', '13', '14', '28'),       ('01', '05', '06', '08', '15', '16'))   I'd like to convert all the string elements into integers and put them back into a list of lists:  T2 = [[13, 17, 18, 21, 32], [7, 11, 13, 14, 28], [1, 5, 6, 8, 15, 16]]   I tried to achieve it with eval but didn't get any decent result yet. I know that for every $n\in\mathbb{N}$, $n\ge 1$, there exists $p(x)\in\mathbb{F}_p[x]$ s.t. $\deg p(x)=n$ and $p(x)$ is irreducible over $\mathbb{F}_p$.     I am interested in counting how many such $p(x)$ there exist (that is, given $n\in\mathbb{N}$, $n\ge 1$, how many irreducible polynomials of degree $n$ exist over $\mathbb{F}_p$).   I don't have a counting strategy and I don't expect a closed formula, but maybe we can find something like "there exist $X$ irreducible polynomials of degree $n$ where $X$ is the number of...".  What are your thoughts ? Another question on almost sure and convergence in probability Convergence in probability implies convergence on a subsequence almost surely.  But this means we fix a subsequence, such that $X_{n_k}$ converges for almost every $\omega$, right? The subsequence we pick does not depend on the $\omega$ right? Native Youtube app suddenly stopped working on iPad 1 It's been some weeks now, whenever I try to used my Youtube app, it tells me it's impossible to connect to Youtube. Since it's an iPad 1, I have had trouble finding information online.  Did Google or Apple stop supporting the app? Is it finally obsolete? Is there another app I could use that works on iOS 5?  Just to be clear, I did not tinker with my device. I did not change its parameters, I did not jailbreak it, it connects to the Internet just fine and I've tried the app on different Internet connections. Also, this is not a login problem, the app just refuses to let me browse videos, whether I'm logged in or not.  Thanks for your help. dd aplied to dev USB before connect corrupt /dev/sdX and dont work So I'm trying to prove the following two inequalities: $$\frac{\sqrt{n}}{2} \leq \phi(n) \leq n.$$ The upper bound we get from simply noting that $\phi(n) = n \prod_{p | n}\left( 1 - \frac{1}{p}\right)$ and the fact that $(1 - \frac{1}{p}) \leq 1$. But how can we get the lower bound? I tried using the same expression for $\phi(n)$ but it seems to not really give me the inequality. Can you help? How do I turn on SharePoint App store in SharePoint 2013 I am getting this message when I want to add a app:     Sorry, apps are turned off. If you know who runs the server, tell them   to enable apps. I want to list a company name in the author field of a bibliographic entry:  @book{CUDA,   author    = {NVIDIA Corporation},   title     = {NVIDIA CUDA Compute Unified Device Architecture Programming Guide},   publisher = {NVIDIA Corporation},   year      = {2007} }   But the entry keeps showing up "N. Corporation".  Is there a way to get the full author name to show up?  I'm currently using the siam BibTEX style. Global setting of spacing between items in itemize environment for beamer How do you iterate through every day of the year? Simplest Example of a Poset that is not a Lattice A partially ordered set $(X, \leq)$ is called a lattice if for every pair of elements $x,y \in X$ both the infimum and suprememum of the set $\{x,y\}$ exists. I'm trying to get an intuition for how a partially ordered set can fail to be a lattice. In $\mathbb{R}$, for example, once two elements are selected the completeness of the real numbers guarantees the existence of both the infimum and supremum. Now, if we restrict our attention to a nondegenerate interval $(a,b)$ it is clear that no two points in $(a,b)$ have either a suprememum or infimum in $(a,b)$.   Is this the right way to think of a poset that is not a lattice? Is there perhaps a more fundamental example that would yield further clarity? How to get permission number by string : -rw-r--r-- What oil is best for seasoning a cast-iron skillet What are Ctools plugin (content type, access, etc), and how does one create them? What are Ctools plugins, and how does one create them? With arrays, why is it the case that a[5] == 5[a]? As Joel points out in , in  (aka: K &amp; R), there is mention of this property of arrays in C: a[5] == 5[a]  Joel says that it's because of pointer arithmetic but I still don't understand. Why does a[5] == 5[a]? Are real guns used in movies? What is the purpose of using a FIFO vs a temporary file or a pipe? Rsync filter: copying one pattern only