[laurentlbm]

I've been using All-In-One Calculator (https://play.google.com/store/apps/details?id=all.in.one.cal...) for years, mostly because of all the conversions it can do. It has what you want, although you need to clear the result before tapping a previous calculation, otherwise it appends the formula to the result (e.g. in your example, you would get 201+1).