We recommend the following motels. Nothing special, but both are good value and are located on Franklin Boulevard, within easy walking distance of the math department. (Cross Franklin to Agate, go one block south on Agate, turn right on 13th Street, then walk through campus to Fenton Hall on the right hand side. If you continue past the front of Fenton Hall, Deady Hall is the next building on the left.)
Best Western Greentree Inn
1759 Franklin Blvd
Eugene, OR 97403.
Best Western New Oregon Motel
1655 Franklin Blvd
Eugene, OR 97440.
A less generic but more expensive option is Excelsior Inn which is located on 13th Street just a couple of blocks west of campus. Another pleasant place to stay is Secret Garden, a bed-and-breakfast style hotel located at 1910 University Street, on the south edge of the campus.
For further information about hotels near campus, you can try the web-site hotels near campus.