Devlins book - "Mathematics: The Science of Patterns" was similar for me and you might enjoy it in addition to what you previously read.

Much better than how I was taught in my schooling.

Toeplitz wrote "Calculus: The Genetic Approach" and his approach of explaining math via its historical development is apparently more widely used: https://en.wikipedia.org/wiki/Genetic_method . Felix Klein remarked: "on a small scale, a learner naturally and always has to repeat the same developments that the sciences went through on a large scale"

I hope it went well! I am in my fifties and enrolled in a master degree program for pure mathematics about 2 years ago (I don't need the degree, so I"m just taking all the classes they offer, so not about to graduate). It definitely took some time to get my brain sharper, but I am better each semester.

I hope people don't take away the negative side of the article, brain slows down, but the positive side: brain gets better with usage. Its uncomfortable, I can churn out programs as complex as programs I've already written and go to review meetings and planning meetings without much effort. But being able to solve PDEs reasonably quickly and accurately, I cannot, or have not without a great deal of practise. It's unconfortable in some weird mental but physical sense. But I'm sharper in everything else I do.

One interesting thing about software as career followed by math classes is that there's no compiler - you can type any janky thought into LaTeX and if you don't detect that it's bogus, nothing will, until you show it to a professor.

Also, the information density of maths notation is way higher than (good) code. We want code to be readable by some that doesn't know it; a lot of math seems to be readable when you sort of 80% already are familiar with all the prereqs. So no just skimming and then hitting compile/test/run (whatever validation you do). It's typing letter by letter and taking the mental effort to actually see and decipher the letter (at least, for me in my current stage; I'm trying to do novel research, but my demonstrated understanding of the details of the previous research is embarrassing low).

Also, weirdly, I still have the same fear of professors that I did as a young person. I manage it better with my decades of maturity (really) but it is still a part of my social interactions.

Do you have a recommendation for a book or course that teaches these things better? In particular FSMs.