Find all the sequences of equal ratios of the form fulfilling the conditions:
- the set is the set of the positive divisors of ;
- the common value of the ratios is an integer.
Solution
The common value of the ratios can be only a divisor of , different from ; these divisors are , , , , , and .
If , then ;
if , then ;
if , then .
There are no other sequences for , or , because if we order decreasingly the divisors and use them one by one, we have to put at the numerator the largest divisor still unused, and at the denominator , getting the sequences from above.
There is no sequence for , respectively , because none of the equalities and , respectively and , can be fulfilled.
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