Stars can fall in one of seven stellar classifications. The constellation Leo contains stars and line segments, as shown in the diagram, with stars connected by line segments having distinct stellar classifications. Let be the number of valid stellar classifications of the stars. Compute the number of positive integer divisors of .
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Solution
1. Understanding the problem: We need to find the number of valid stellar classifications for the 9 stars in the constellation Leo, where each star has a distinct classification from its connected stars. Then, we need to compute the number of positive integer divisors of this number.
2. Analyzing the pentagon subset: Consider the 5-star pentagon subset of the constellation, denoted as . We need to classify these stars such that no two connected stars have the same classification.
3. **Classifying and **: There are 7 possible classifications for and 6 remaining classifications for , giving us ways to classify and .
4. **Classifying :
- Case 1**: has the same classification as or . There are 2 choices for (same as or ), 6 choices for (different from and ), and 5 choices for (different from , , and ). This gives ways.
- Case 2: has a different classification from and . There are 5 choices for , 5 choices for (different from , , and ), and 5 choices for (different from , , , and ). This gives ways.
5. Total classifications for the pentagon: Summing the two cases, we get ways to classify the pentagon given the classifications of and . Therefore, the total number of valid classifications for the pentagon is .
6. Classifying the remaining 4 stars: Each of the remaining 4 stars can be classified in 6 ways (since they are connected to at most 3 other stars, and there are 7 classifications in total). Thus, the total number of valid classifications for the entire constellation is:
7. Finding the number of positive integer divisors: To find the number of positive integer divisors of , we need its prime factorization:
The number of positive integer divisors is given by multiplying the incremented exponents:
The final answer is