Take a look at the 2 listed references by Parks and McClellan. They are considered seminal papers in the field of signal processing and are the basis of the fun

Take a look at the 2 listed references by Parks and McClellan. They are considered seminal papers in the field of signal processing and are the basis of the function you linked. And they will probably appeal to your math background more. The name of the algorithm is Parks McClellan filter design, or sometimes you will see it named firpm, as popularized by MATLAB. https://en.wikipedia.org/wiki/Parks%E2%80%93McClellan_filter_design_algorithm#:~:text=The%20Parks%E2%80%93McClellan%20algorithm%2C%20published,efficient%20and%20optimal%20FIR%20filters https://en.wikipedia.org/wiki/Parks%E2%80%93McClellan_filter....