Remove stones
Posted: January 16th, 2008, 9:25 am
I found this teaser recently, anyone will suggest a clue to trackle it. Forgive me if it has bee posted before.Alice and Bob play a game in which they take turns removing stones from a heap that initially has n stones.The number of stones removed at each turn must be one less than a prime number. The winner is the player whotakes the last stone. Alice plays first. Prove that there are infinitely many n such that Alice has a winning strat-egy. (For example, if n = 17, then Alice might take 6 leaving 11; then Bob might take 1 leaving 10; thenAlice can take the remaining stones to win.)