18 Answers votes newest views recent 4What should be offered in undergraduate mathematics that’s currently not (or isn’t usually)? 2Most helpful math resources on the web 1What do you call the product of a circle and an annulus? 0Learning Topology 6Introductory text on geometric group theory? 2Nice proof of the Jordan curve theorem? 1HNN extensions which are free products 18books well-motivated with explicit examples (3) -1less elementary group theory 16Which mathematicians have influenced you the most? 1Undergraduate Differential Geometry Texts 1Memorizing theorems -2Canonical examples of algebraic structures 2Circle bundles over $RP^2$ 1What is the first interesting theorem in (insert subject here)? 0Algorithmic Combinatorics resources? 0de Rham Cohomology of surfaces 3Great mathematical figures and/or diagrams?