Great idea to compile this list. One of my favourite mathematics books that is available for free download is GeneratingFunctionology - https://www.math.upenn.e

Great idea to compile this list. One of my favourite mathematics books that is available for free download is GeneratingFunctionology - https://www.math.upenn.edu/~wilf/DownldGF.html https://www.math.upenn.edu/~wilf/DownldGF.html Well-written and incredibly rewarding.