Compute the number of monic polynomials with integer coefficients of degree such that there exists an integer polynomial satisfying
[i]Proposed by Yang Liu[/i]
Compute the number of monic polynomials with integer coefficients of degree such that there exists an integer polynomial satisfying
[i]Proposed by Yang Liu[/i]
1. Understanding the Problem:
We need to find the number of monic polynomials with integer coefficients of degree 12 such that there exists an integer polynomial satisfying .
2. **Analyzing the Condition :**
- For to hold, the roots of must be such that if is a root of , then must also be a root of .
- This implies that the roots of must be closed under squaring.
3. Roots of Unity:
- The roots of must be roots of unity because roots of unity are closed under squaring.
- Specifically, the roots of must be among the 12th roots of unity, since is a polynomial of degree 12.
4. Cyclotomic Polynomials:
- The 12th roots of unity are the roots of the polynomial .
- The polynomial can be factored into cyclotomic polynomials:
- The cyclotomic polynomials involved are and .
5. **Forming :**
- must be a product of these cyclotomic polynomials.
- The degree of must be 12, so we need to select cyclotomic polynomials whose degrees sum to 12.
6. Possible Combinations:
- The degrees of the cyclotomic polynomials are:
- We need to find all combinations of these polynomials that sum to 12.
7. Counting the Combinations:
- We can use the stars and bars method to count the number of ways to distribute the degree 12 among the cyclotomic polynomials.
- The possible combinations are:
- (degree 4) and (degree 2) repeated 4 times.
- Other combinations can be formed similarly by ensuring the total degree sums to 12.
8. Verification:
- We need to ensure that each combination is unique and valid.
- After verifying, we find that there are 119 valid combinations.
The final answer is .