Not at all what I'm looking for. There's no nice mobile spreadsheet software and if I have a laptop with me, I'd much rather use something like Mathematica or M

Not at all what I'm looking for. There's no nice mobile spreadsheet software and if I have a laptop with me, I'd much rather use something like Mathematica or Maxima or Octave or Python+SciPy or Gnuplot depending on the task at hand. Excel doesn't do symbolic computation and it's rather clumsy for dealing with mathematical expressions rather than arrays of numbers. Although I must admit that I'm not very good with Excel, perhaps it would be useful to spend some time with it (or the LibreOffice equivalent). For some basic tasks, I can get along with Wolfram Alpha mobile app (it does plots and symbolic integration/differentiation), but it's not very good for long calculations where I need to store results from previous calculations.