Find the largest positive integer such that the residue of when divided by each perfect square between and is an odd number.
Solution
1. Identify the problem constraints:
We need to find the largest positive integer such that the residue of when divided by each perfect square between and is an odd number.
2. Reformulate the problem:
We need to ensure that for every perfect square where , the residue is odd.
3. Consider the range of perfect squares:
We need to find odd perfect squares between and . If such a square exists, then we can write where is the residue.
4. Analyze the residue:
Since is odd, must be even. This is because is odd (as is odd), and the sum of an odd number and an even number is odd.
5. **Estimate :**
For sufficiently large , there exists an odd square between and . We need to find such an .
6. Check specific values:
Let's check :
- The range for perfect squares is between and .
- The odd perfect squares in this range are (which is ) and (which is ).
7. Verify the residues:
- For , (odd).
- For , (not odd).
8. **Adjust :**
Since is not odd, we need to find a larger that satisfies the condition for all perfect squares in the range.
9. **Find the correct :**
After further checking, we find that satisfies the condition:
- The range for perfect squares is between and .
- The odd perfect squares in this range are and .
- For , (odd).
- For , (even).
10. Conclusion:
The largest that satisfies the condition is .
The final answer is .