I don't know any calculus but I'm pretty sure it's what I need to figure out an equation I need for a blog post I'm working on. Here's the blog post. http://ratdog-justbecause.blogspot.com/2015/01/low-eroei-and-low-power-density-is.html . I think maybe what I'm looking for is the Σ as n approaches infinity for 1/xn. With n starting out as 0. I don't really know for sure though. Any help is appreciated. Thanks.