Select every n-th verticle

Hi,

Let’s say I have a sphere with 100 segments and 100 rings. I would like to select (for example) every second segment or every third but somehow automatically. Is there any way to do it in Blender or I have to do it manually (with alt pressed and clicking every second/third segment)?

Here is the example of what I want to achieve automatically:

https://googledrive.com/host/0B4dXSfSRfzLcUGF5MGRDTjNiUWc/Untitled-1.jpg