In how many ways can the number be represented as a product of two fractions of the form , where is a positive integer? (Order of the factors is not important.)
Solution
Let and be positive integers such that .
Then i.e. .
From the last equation we find
Since and are positive integers, it follows that is a positive divisor of . Each divisor of corresponds to exactly one pair . Since , the number of its divisors is . Finally, since the pairs and determine the same representation, the number of required representations is 16.
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