MAT 503 is an introduction (at the graduate level) to Complex Analysis, one of the most beautiful subjects in all of mathematics. Topics include: differentiability of complex functions, complex integration and Cauchy's theorem, series expansions, calculus of residues, conformal mapping, and time permitting, the Prime Number Theorem.
Complex Analysis; Elias M.Stein & Rami Shakarchi. Princeton Lectures in Analysis
Mathematical maturity