Welcome to Week 3 of "Analytic Combinatorics." This week, we introduce the idea of viewing generating functions as analytic objects, which leads us to asymptotic estimates of coefficients. The approach is most fruitful when we consider GFs as complex functions, so we introduce and apply basic concepts in complex analysis. We start from basic principles, so prior knowledge of complex analysis is not required. ---------- Lecture 4: Complex Analysis, Rational and Meromorphic Asymptotics. We consider basic principles of complex analysis, including analytic functions (which can be expanded as power series in a region); singularities (points where functions cease to be analytic); rational functions (the ratio of two polynomials) and meromorphic functions (the ratio of two analytic functions). The heart of the matter is complex integration and Cauchy's theorem, which relates coefficients in a function's expansion to its behavior near singularities. The discussion culminates in a general transfer theorem that gives asymptotic values of coefficients for meromorphic (and rational) functions. ---------- There are two clusters of errata in this lecture. See ACqa3.pdf for details. Your assignment for this week, due at 11:59PM on Thursday, April 7, 2022 is to write up and submit solutions to Web Exercise IV.2 and Note IV.28 on the "Analytic Combinatorics" booksite. For extra credit, do Program IV.2. If you're more comfortable with some other package for plotting complex functions, feel free to use it. As usual, submit a potential exam question on the week's material. Submit files named "AC3-Q1.pdf" "AC3-Q2.pdf" "AC3-Q3.pdf" (optional extra credit) "AC3-QQ.pdf" via codePost. RS