Let us denote by and the largest and the smallest prime divisors of , respectively. Alireza and Amin decided to play the following game. Starting with Alireza, he chooses 1400 polynomials with integer coefficients. Then, Amin chooses 700 polynomials among them and denotes their sets by and , respectively. Amin shall win the game if for each positive integer
otherwise, Alireza shall win the game. Which player has the winning strategy?
Solution
Let us denote by all the 700-element subsets of . Let . Now, choose 1400 polynomials of the following form:
We now claim that if Alireza chooses these 1400 polynomials, he shall win the game. Assume that Amin chooses 700 polynomials . Let us denote by the set . Then, for all we have hence . Otherwise, then and hence .
Hence, for ;
Thus, by choosing such polynomials, Alireza shall win.
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