This dataset contains 27000 images of 18 handwritten mathematical symbols (1500 images per symbol). The symbols are: 0,1,2,3,4,5,6,7,8,9,*,-,+,/,w,x,y,z.
You can find the symbols in the symbols directory. Each file has the following format: <symbol-name>-<id>.png, e.g. slash-1484.png.
The data was initially gathered for use in the camculator project. We couldn't find a dataset that would suit our needs, which were digits (MNIST covers this case), some letters (Extended MNIST is fine) and symbols like / and + (we couldn't find any dataset of high quality and quantity for this case).
It was gathered by having a couple of people (hence the writing style is not very diverse - sorry about that!) fill numerous sheets of paper with handwritten symbols. We later took the photos of the sheets and put the pictures in a simple processing pipeline which extracted digits automagically, cropping them and scaling to the desired resolution. We later filtered out any trash outputs.
Feel free to use this dataset, it's licensed under the MIT License.