I am having trouble understanding this question. By the words "mathematical concentrations", could one substitute the term "mathematical subfields"
Yes, thank you, I performed the substitution in the original post.
If so, then I would say the best resource could be more experienced people with similar instrumental goals to one's self.
Which is precisely why I am asking LessWrong.
So, is your goal to build an AGI? If so, you should email "yudkowsky@gmail.com".
There is, of course, Kahn Academy for fundamentals. We have already had a discussion on How to learn math.
What resources exist detailing which mathematics to learn in what order? What resources exist that explain the utility of different mathematical subfields for the purpose of directing studies?