1. Define the problem and notation:
We need to determine the maximal number of consecutive interesting integers. An integer k is interesting if the product of the first k primes is divisible by k. Let pn denote the n-th smallest prime number. For example, p1=2, p2=3, p3=5, and so on.
2. **Check small values of k:**
- For k=1, the product of the first 1 prime is p1=2, and 2 is divisible by 1. Hence, 1 is interesting.
- For k=2, the product of the first 2 primes is p1⋅p2=2⋅3=6, and 6 is divisible by 2. Hence, 2 is interesting.
- For k=3, the product of the first 3 primes is p1⋅p2⋅p3=2⋅3⋅5=30, and 30 is divisible by 3. Hence, 3 is interesting.
- For k=4, the product of the first 4 primes is p1⋅p2⋅p3⋅p4=2⋅3⋅5⋅7=210, and 210 is not divisible by 4. Hence, 4 is not interesting.
3. Generalize the observation:
- For k=5, the product of the first 5 primes is p1⋅p2⋅p3⋅p4⋅p5=2⋅3⋅5⋅7⋅11=2310, and 2310 is divisible by 5. Hence, 5 is interesting.
- For k=6, the product of the first 6 primes is p1⋅p2⋅p3⋅p4⋅p5⋅p6=2⋅3⋅5⋅7⋅11⋅13=30030, and 30030 is divisible by 6. Hence, 6 is interesting.
- For k=7, the product of the first 7 primes is p1⋅p2⋅p3⋅p4⋅p5⋅p6⋅p7=2⋅3⋅5⋅7⋅11⋅13⋅17=510510, and 510510 is divisible by 7. Hence, 7 is interesting.
- For k=8, the product of the first 8 primes is p1⋅p2⋅p3⋅p4⋅p5⋅p6⋅p7⋅p8=2⋅3⋅5⋅7⋅11⋅13⋅17⋅19=9699690, and 9699690 is not divisible by 8. Hence, 8 is not interesting.
4. Conclusion:
From the above steps, we observe that the maximal number of consecutive interesting integers is 7.
The final answer is 7.