I deleted my question from Stack Overflow. How can I delete the revision history? I deleted my question from Stack Overflow having some sensitive information, but I believe the question is not completely removed from Stack Overflow. It also has a revision history, so I want to remove all the data related to it - snapshot everything. Could anyone properly help me to resolve this matter?
What should I do if a user posts sensitive information as part of a question or answer? I've observed several incidents where users inadvertently posted detailed, sensitive information. For example, a Server Fault user who posted a question with working login credentials to his actual production server, or the Stack Overflow user who posted actual medical records as example data for his question.   What should be the procedure for handling such cases?
Explicit formulas for Stirling numbers of second kind I have seen some recursive formulas for Stirling I and II kind but I am especially interested in explicit formulas.  I was thinking and get: $$ \left\{ {m \atop n} \right\} =  \sum_{k_i&gt;0 \wedge k_1+k_2+...+k_n = m} \frac{m!}{n!}\cdot \frac{1}{k_1! \cdot k_2! \cdot ... \cdot k_n!}$$ I am not sure if it is ok but supposedly it is (I created it with combinatorics interpretation)  Can somebody look at that and tell me if it is ok/wrong?  By the way,if you have some nice formulas, I will be grateful for sharing that. How to avoid perceived circularity when defining a formal language? Suppose we want to define a first-order language to do set theory (so we can formalize mathematics). One such construction can be found . What makes me uneasy about this definition is that words such as "set", "countable", "function", and "number" are used in somewhat non-trivial manners. For instance, behind the word "countable" rests an immense amount of mathematical knowledge: one needs the notion of a bijection, which requires functions and sets. One also needs the set of natural numbers (or something with equal cardinality), in order to say that countable sets have a bijection with the set of natural numbers.  Also, in set theory one uses the relation of belonging "$\in$". But relation seems to require the notion an ordered pair, which requires sets, whose properties are described using belonging...  I found the following in Kevin Klement's,  (pages 2-3).  "You have to use logic to study logic. There’s no getting away from it. However, I’m not going to bother stating all the logical rules that are valid in the metalanguage, since I’d need to do that in the metametalanguage, and that would just get me started on an infinite regress. The rule of thumb is: if it’s OK in the object language, it’s OK in the metalanguage too."  So it seems that, if one proves a fact about the object language, then one can also use it in the metalanguage. In the case of set theory, one may not start out knowing what sets really are, but after one proves some fact about them (e.g., that there are uncountable sets) then one implicitly "adds" this fact also to the metalanguage.  This seems like cheating: one is using the object language to conduct proofs regarding the metalanguage, when it should strictly be the other way round.  To give an example of avoiding circularity, consider the definition of the integers. We can define a binary relation $R\subseteq(\mathbf{N}\times\mathbf{N})\times(\mathbf{N}\times\mathbf{N})$, where for any $a,b,c,d\in\mathbf{N}$, $((a,b),(c,d))\in R$ iff $a+d=b+c$, and then defining $\mathbf{Z}:= \{[(a,b)]:a,b\in\mathbf{N}\}$, where $[a,b]=\{x\in \mathbf{N}\times\mathbf{N}: xR(a,b)\}$, as in  question or  on Wikipedia. In this definition if set theory and natural numbers are assumed, then there is no circularity because one did not depend on the notion of "subtraction" in defining the integers.  So my question is:     Question Is the definition of first-order logic circular?   If not, please explain why.   If the definitions are circular, is there an alternative definition which avoids the circularity?   Some thoughts:   Perhaps there is the distinction between what sets are (anything that obeys the axioms) and how sets are expressed (using a formal language). In other words, the notion of a set may not be circular, but to talk of sets using a formal language requires the notion of a set in a metalanguage. In foundational mathematics there also seems to be the idea of first defining something, and then coming back with better machinery to analyse that thing. For instance, one can define the natural numbers using the Peano axioms, then later come back to say that all structures satisfying the axioms are isomorphic. (I don't know any algebra, but that seems right.) Maybe sets, functions, etc., are too basic? Is it possible to avoid these terms when defining a formal language? I have a list of Line_item__c which is storing my line items as  List&lt;Line_Item__c&gt; toInsertList = new List&lt;Line_Item__c&gt;();   I am inserting these records in database using the below statement :  List&lt;Database.Saveresult&gt; insertResults=Database.insert(toInsertList, false);   Now the result is stored in insertResults which is of Database.Saveresult type but i want the result in a list of Line_Item__c. How do i do this. If anyone has a idea, it will be of great use. Search results on https://stackexchange.com are broken because of "insecure content" The search results on  are blocked because of:     [blocked] The page at  ran   insecure content from .   I am using Chrome. Useless math that became useful I'm writing an article on  and some people pointed out that this is completely useless.  My idea is to amend my article with some theories that seemed useless when they are created but found use after some time.  I came with some ideas like the Turing machine but I think I'm not grasping the right examples.  Can someone point me some theories that seemed like the Lychrel numbers and then become 'useful'? proving of inequality $(n!)^2 \leq n^n\cdot n!\leq (2n!)$, where $n\in \mathbb{N}$ How can we prove the inequality $(n!)^2 \leq n^n\cdot n!\leq (2n!)$, where $n\in \mathbb{N}$  $\bf{My \; Try}$::  $1\leq n$  $2\leq n$  $3\leq n$  ....  ....  $n\leq n$  So $1\cdot 2 \cdot 3 ..n \leq n^n$  So $n!\leq n^n\Rightarrow (n!)^2 \leq n^n\cdot n!$  But  did not understand how can we prove $n^n\cdot n! \leq (2n!)$  Help me  Thanks Why do I have blurred vision and how do I fix it? ASP.NET MVC Default Project Structure and the Scripts Folder Merge multiple video with ffmpeg single command line in specific time without cut it one by one and merge it I have 15 video files which I want to merge with ffmpeg. I want to save time by merge all of the video files in a single command line, not cut it one by one and merge it. Thanks. I am on SharePoint 2013 and do not have access to Designer, as a preface.  I am trying to create a list view that filters items by whether or not they were added in the last hour.  I had done this earlier, only with items that were added in the current week, by creating two columns, 'Week Start' and 'Week End', and filtering by Created falling between those two.  Simple enough.  However, filtering list views does not allow for complex functions, nor does the [Today] function recognize time, causing an issue.  Is there any workaround for this?  Thanks. I ran into an interesting (and very frustrating) issue with the equals() method today which caused what I thought to be a well tested class to crash and cause a bug that took me a very long time to track down.   Just for completeness, I wasn't using an IDE or debugger - just good old fashioned text editor and System.out's. Time was very limited and it was a school project.  Anyhow -   I was developing a basic shopping cart which could contain an ArrayList of Book objects. In order to implement the addBook(), removeBook(), and hasBook() methods of the Cart, I wanted to check if the Book already existed in the Cart. So off I go -  public boolean equals(Book b) {     ... // More code here - null checks     if (b.getID() == this.getID()) return true;     else return false; }   All works fine in testing. I create 6 objects and fill them with data. Do many adds, removes, has() operations on the Cart and everything works fine. I read that you can either have equals(TYPE var) or equals(Object o) { (CAST) var } but assumed that since it was working, it didn't matter too much.  Then I ran into a problem - I needed to create a Book object with only the ID in it from within the Book class. No other data would be entered into it. Basically the following:  public boolean hasBook(int i) {     Book b = new Book(i);     return hasBook(b); }  public boolean hasBook(Book b) {     // .. more code here     return this.books.contains(b); }   All of a sudden, the equals(Book b) method no longer works. This took a VERY long time to track down without a good debugger and assuming the Cart class was properly tested and correct. After swaapping the equals() method to the following:  public boolean equals(Object o) {     Book b = (Book) o;     ... // The rest goes here    }   Everything began to work again. Is there a reason the method decided not to take the Book parameter even though it clearly  was  a Book object? The only difference seemed to be it was instantiated from within the same class, and only filled with one data member. I'm very very confused. Please, shed some light? How to pick a specific symbol from a specific font? Using Custom Labels in a Class I have the below If statements using some hard coded strings and I want to make them use as custom labels. I have created custom labels with the same String names as given below. So how can I make these statements to use the Custom Labels I created ?  if(monitoringFrequency == 'daily'){             return dateValue.addDays(1);         }else if(monitoringFrequency == 'weekly'){             return dateValue.addDays(7);         }else if(monitoringFrequency == 'monthly'){             return dateValue.addMonths(1); Question about Riemann integral and total variation What does '>/dev/null 2>&1' mean in this article of crontab basics? How to make Blender use Python2.x? Area is calculating wrong using $area in field calculator (QGIS 2.8.1-Wien) How to get a drive formatted with exfat working? In Bishop's book "Pattern Classification and Machine Learning", it describes a technique for regularization in the context of neural networks. However, I don't understand a paragraph describing that during the training process, the number of degrees of freedom increases along with the model complexity. The relevant quote is the following:     An alternative to regularization as a way of controlling the effective   complexity of a network is the procedure of early stopping. The   training of nonlinear network models corresponds to an iterative   reduction of the error function defined with respect to a set of   training data. For many of the optimization algorithms used for   network training, such as conjugate gradients, the error is a   nonincreasing function of the iteration index. However, the error   measured with respect to independent data, generally called a   validation set, often shows a decrease at first, followed by an increase as the network starts to over-fit. Training can therefore be   stopped at the point of smallest error with respect to the validation   data set, as indicated in Figure 5.12, in order to obtain a network   having good generalization performance. The behaviour of the network   in this case is sometimes explained qualitatively in terms of the   effective number of degrees of freedom in the network, in which this   number starts out small and then to grows during the training process,   corresponding to a steady increase in the effective complexity of the   model.   It also says that the number of parameters grows during the course of training. I was assuming that by "parameters", it refers to the number of weights controlled by the network's hidden units. Maybe I'm wrong because the weights are prevented to increase in magnitude by the regularization process but they don't change in number. Could it be referring to the process of finding a good number of hidden units?  What's a degree of freedom in a neural network? What parameters increase during  training? Sum of infinite series $\sum_{i=1}^{\infty} \frac 1 {i(i+1)(i+2)...(i+n)}$ Lets define the following series $$S_n =\sum_{i=1}^{\infty} \frac 1 {i(i+1)(i+2)...(i+n)}.$$ I know that $S_0$ does not converge so let's suppose $n \in N$ and define $S_n$ for some $n$. We have $S_1=1$ , $S_2=\frac1 4$ , $S_3=\frac 1 {18}$ , $S_4=\frac 1{96}$ , $S_5=\frac 1{600}$ etc.. the numerator in all results is 1the pattern in denominator is $[1,4,1,96,600...]$ and   that is equal to $n*n!$ Finally I want to prove the general equality: $\sum_{i=1}^{\infty} \frac 1 {i(i+1)(i+2)...(i+n)}=\frac 1 {n*n!}$