Title: 1+2+3+4+… = -1/12 Abstract: Infinite series. Every Calculus II student hates them; every mathematician loves them. So, why do mathematicians love infinite series? Well, ask one, and you’ll never hear the end of it… (just sum math humor). We’ll see how two standard examples of series, the geometric series and the zeta function (p-series), lead to beautiful applications, such as in economics and signal processing. We’ll also see how even divergent series are fascinating.