The Institute of Mathematics is part of the Wechloy Campus and is thus located at Carl von Ossietzky Straße 9-11.
Take the A28 motorway to the Haarentor exit, drive out of town until you see a car dealership (Mercedes Senger) on the right and turn right (Carl-von-Ossietzky Straße). Follow the road and keep left at the fork. The Institute of Mathematics is located in the larger building. At the main entrance, turn left up the stairs and then left through the glass door. There is a signpost to the individual rooms on the staircase there. (Further information can be found on the access page of the university.)
Two bus lines run from the bus stop behind the station to the university. These are line 306 (towards the university) to the mathematics/natural sciences site (terminus), but only until about 7 pm, and line 310 (towards Wehnen). The latter stops at Grotepool (Mercedes Rosier), from there it is about a 5-minute walk. At the pedestrian lights, take the uphill footpath on the right, at the end of which turn left. The path then leads directly to the Wechloy university building, which houses the mathematics department. At the main entrance, turn left up the stairs and then left through the glass door. (For more information, see the university's access page.)
To get behind the station, use the north exit and not the way to the main exit of the station.