First it's Feynman with one <n>. Second, his famous lectures from '62 which are found in printed form are delivered to an audience of college students, not HS. Thus the mathematics involved is typically college (partial derivatives, multiple integrals, differential equations, linear algebra for QM part,...).
BUT there are chapters especially in the first 2 volumes which use HS mathematics and can be read & understood by an HS student, which is why it's recommendable to read them before going to college.