Reinstalling new server

The seed is stored per world. If you reinstall the server, it depends on whether the "Worlds" folder (and the server.properties file) were deleted. The active world is determined by the server.properties file (it's the "World_Name" entry). If that world still exists in the "Worlds" folder, it will still be loaded when starting the server.

If the server.properties file was deleted but the world is still there, just enter the world name there to instruct the server to load it

Quote from icon58

So if you do a clean, fresh. totally wipe the server does that give you a new seed?

It depends on whether or not you delete the "Worlds" folder (in the server directory). If you delete it, the server will create a new world based on the seed provided in the server.properties file (the setting called "World_Seed"). If this entry is blank (default), it will create a world with a random seed.