I'm a 3rd year physics undergrad, currently taking a first compulsory course in statistical mechanics. The course follows R. Kubo's text of the same title along with additional lecture notes given in class(theory on ensembles and such). The highest level mathematics any of my classmates have taken is PDE's/integral transforms & ODEs/complex analysis. The prior courses in linear algebra and calculus were a lot more rigorous and proof-based (Spivak/Apostol for example). We have dealt with/proven special function relations like the Gamma, Beta and erf functions in our last calculus courses and have had exposure to Legendre, Bessel, Hermite, ... etc. polynomials as a basis for DE solutions in both physics and math courses. However now we are being faced with problems that require math tools that are unknown to anyone in the class. Among them are several problems that involve determining the thermodynamic weight (in other words: state density) for a system using combinatorics (never studied it before, at best a few of us know that you can order 3 books in 3 spaces in 3! ways. No idea how to generalize that to N books with "up or down" degree of freedom into M spaces), proving Stirling's formula for logs of factorials, proving Euler-McLaurin's formula, among a few other things. I've been asking around and none of my classmates know how to do these things... but we're still plowing through the assigned problems (mostly from Kubo's book) without stopping other than to discuss the physical significance of a solution (which is great, but no physical reasoning is going to get me the correct factorial expression for the state density). It is worth mentioning that the undergrad program just got restructured and one compulsory "math methods for physicists" (group theory, integral equations, combinatorics & probability) course got dropped from the curriculum, however my professor seems to be up to date on our curriculum so I don't think this is unintentional. Is this excessive? What should I do to get up to speed in these areas, combinatorics in particular (as it has shown up the most in problems so far)? Should I be expressing these concerns to my professor about a month away from the final exam? (we started doing problems quite late into the course, the first half was all theory).