5 Hitch Your Spaceship to a Star

From www.donaldwestlake.com

Then, one day in the year eleven thousand four hundreds and six (11, 406), an incredible discovery was made in the Master Imperial Computer back on Earth. Nearly 500 years before, a clerical error had erased from the computer’s memory more than 1000 colonies, all in sector F.U.B.A.R. 3. For half a millenium, those colonies, young and struggling when last heard from, had had no contact with the rest of humanity.