Starting with a 100 Grid, the first player chooses a positive even number that is less than 50, and crosses it out on the grid. The second player chooses a number to cross out. The number must be a factor or multiple of the first number.
Players continue to take it in turns to cross out numbers, at each stage choosing a number that is a factor or multiple of the number just crossed out by the other player. The first person who is unable to cross out a number loses.