A digital notebook for Mathematics? When I studied math 15 years ago, I was dreaming of having a math repository with tags to navigate between the different entries.
I imagined it would come eventually to the market, and was hopefull when I saw the TabletPC included handwriting recognition of equation, and a few software like mathjournal came to fruition using it. then I stopped watching.
Are there any practical solution today to gather mathematical notes?
I take pictures of my handwritten notes in Evernote, but there must be some better and more natural ways to collect notes.
Ideally, the solution would be :


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*handwritten input, but with text/equation recognition for rewriting

*synchronized across my devices

 A: I have a couple friends who take notes with their IPads, and it seems very well suited for the task. There is a journal that takes very clean math notes, which one can organize into books, chapters, and with tags, etc. Also, I'm given to understand that there's a feature where one can convert the notes into searchable PDFs. 
A: I have a tablet PC (HP tc4200) which I bought refurbished off Newegg (~$250).  I installed Ubuntu on it and take notes in Xournal.  I store the notes in Dropbox, and often export to pdf, so I can access them from any computer with a pdf reader.  (Here is an example.)  I am very happy with this setup; the program works well, Ubuntu has proper driver support for the touchscreen, and the 
While I was making the decision, I weighed between a slate tablet and a tablet PC.  An older tablet PC is heavier than a slate like the iPad, and it's definitely not as sexy, but it has about the same processing power, much more storage space, and it has significantly more screen real estate, which is a big plus in my eyes.  Of course, there's also the fact that you can get an older one refurbished for a little more than half the price of an iPad.
(Also, for what it's worth, I have a friend who bought a Galaxy last summer.  He tells me that android note-taking apps are at the moment far inferior to iPad note-taking apps.)
A: Yes, there is as I show with my answer here and check the recommended apps here -- particularly, I think the Paper 53 -app in iPad acts like a "digital notebook".
Notes into searchable books


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*UPad for note-taking, very good sharing and very good tiny-writing


*Evernote-or-some-other-thing for search


**ix -commands here to make PDF -books from your notes

Unsolved OCR -problem

The recognition problem is still under heavy creative research, more here and here. In other words, it is not yet solved and most softwares you are going read below lack the advanced OCR -support -- it is possible nowadays to get it working linewise like here -- more with search-terms such as Stefan Knerr (CEO of Vision Objects, they did the prototype), the paper "Recognition-directed recovering of temporal information from handwriting images" and its successor "Combining diverse systems for handwritten text line recognition" (2011).
You can consult more this problem here and perhaps here. I am still working on them.

General threads about Digital Notebook for Mathematics


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*Kindle as a Tool for Mathematicians?


*Tablet for reading textbooks and writing math by hand?


*Similar question in Math Overflow here (a lot of confusing outdated material).

