The method of proportional representation used in the European elections seems particularly complicated.
The party with the highest number of votes gets one seat allocated in round 1. For round 2 this party has its vote divided by two. The party with the highest vote in round 2 is then allocated a seat and its vote is divided by two.
If a party which has already won a seat wins another round its vote is divided by the number of seats it has won plus one. This continues until all the seats have been allocated