Adsense after random post

Hi there,

I know how to insert adsense after a particular post and it shows up there every time. However, it would be a way better and more effective for my blog if I could insert ads after random post.

Let’s say I have 6 posts per every page. I would like adsense to appear after a different post every time visitor goes to another page or refreshes it. It would also work if I could define several values (after 1, 3 and 5 post for example) and adsense would appear in one of these positions randomly.

Is there a way/a code/a plugin to do this? Thank you.