Arithmetic progression game
This article relies on a single source. (January 2019) |
In combinatorial game theory, an arithmetic progression game is a positional game where two players alternately pick numbers, trying to occupy a complete arithmetic progression of a given size.
The game is parameterized by two integers . The game-board is the set . The winning-sets are all the arithmetic progressions of length . In a Maker-Breaker game variant, the first player (Maker) wins by occupying a -length arithmetic progression, otherwise the second player (Breaker) wins.
The game is also called the van der Waerden game,[1] named after Van der Waerden's theorem. It says that, for any , there exists some integer such that, if the integers are partitioned arbitrarily into two sets, then at least one set contains an arithmetic progression of length . This means that, if , then Maker has a winning strategy.
This claim is not constructive - it does not show a specific strategy for Maker. Moreover, the current upper bound for is extremely large: the currently known bounds are for every .
Let be the smallest integer such that Maker has a winning strategy. Beck[1] proves that . In particular, if , then the game is Maker's win (even though it is much smaller than the number that guarantees no-draw).