rehiring with the same manager is very rare - when an employee leaves on their own its an automatic red mark against a managers review. At some level it is the employee firing the company.
So you can do the decent thing (we will all meet god for our day of judgement) and give 3 weeks but just be prepared to get walked (take your personal stuff home beforehand so its quick and easy on you) - not a lot of managers will do the decent thing in return in my experience - not a lot will even do the decent thing and box up your personal stuff and send it to you even - they'll just dispose of everything and claim they didn't realize it was yours. These days the only guys I see not getting walked are retirees or those obviously changing into something that is different.