Show that there exist consecutive positive integers such that for each of them the ratio between the largest and the smallest prime divisor is more than
Solution
1. Define the Primes:
Let be the first 2009 prime numbers. Let be another set of prime numbers such that for all . This is possible because there are infinitely many primes, and for any prime , there exists a prime such that .
2. Chinese Remainder Theorem:
By the Chinese Remainder Theorem, there exists an integer such that:
This is possible because the moduli are pairwise coprime.
3. Consecutive Integers:
Consider the sequence . For each in this range, is divisible by . Therefore, the smallest prime divisor of is and the largest prime divisor is .
4. Ratio of Prime Divisors:
For each , the ratio between the largest and the smallest prime divisor is:
This satisfies the condition that the ratio between the largest and the smallest prime divisor is more than 20.
5. Conclusion:
Thus, the sequence consists of 2009 consecutive positive integers such that for each of them, the ratio between the largest and the smallest prime divisor is more than 20.