Thomas Edison State College offers a BA in Mathematics, and has quite a few upper-level classes that you can use to satisfy the requirements. Excelsior College has both a BA and BS in Mathematics, but you will need to take some classes elsewhere to complete it. I'm sure there are others, too; Googling something like "site:edu online bachelor mathematics" might turn up some leads.
Personally, I would look at U-Illinois-Springfield or U-Arkansas-Litte Rock. When going the online route, I would recommend branch campuses of bigger state schools.
