Not that I know of. If you purchase an app, you can download it to an unlimited number of iDevices. That is true - with the only caveat being that you MUST use the same Apple ID and iTunes account each time you download it.
So you will have no problem downloading the app to the 13 iPads with your account. However, that purchase is ALWAYS tied to your Apple ID and iTunes account. It can't be transferred to another user or to another iTunes account.
The app will be usable on the 13 iPads but if the app needs to be updated, the users of those 13 iPads will have to sign in with your ID to update the app. This can be done directly on the iPad, but you probably don't want to give your ID and password out to those 13 individuals and you won't want to have to update each of their iPads every time by signing in with your ID and then have to sign out again.
On top of that, if the 13 users will want to sync to their own computers that contain their own iTunes libraries, that app will not sync - it will be erased if not mistaken - if they as they will be signed in with their own accounts.
If I may ask, what app and what are you trying to accomplish by doing this - what is the bigger picture so to speak?