This article is rated Stub-class on Wikipedia's content assessment scale. It is of interest to the following WikiProjects:

Mathematics Low‑priority This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.MathematicsWikipedia:WikiProject MathematicsTemplate:WikiProject Mathematicsmathematics articles Low This article has been rated as Low-priority on the project's priority scale. Robotics Mid‑importance This article is within the scope of WikiProject Robotics, a collaborative effort to improve the coverage of Robotics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.RoboticsWikipedia:WikiProject RoboticsTemplate:WikiProject RoboticsRobotics articles Mid This article has been rated as Mid-importance on the project's importance scale.

I added a stub tag. If any knows a good stub category, feel free to add it.

I think it needs some equations, and an example with a typical N, and some history and references, for readers like me who want to know more about it.

Dicklyon 15:49, 7 September 2006 (UTC) reply