1008 B
Here we brute-force through every possible denominator d (from 1 to 12000).
For every denominator the valid numerators are between floor(d/3) and ceil(d/2).
The only problem is that we don't know if a fraction is proper.
To solve this we use a 12000x12000 array where we mark the already found fractions and every multiple of them.
When we now find a new one we can test if we have already found the fraction (in a reduced form).
But a 12000x12000 array is quite big, the resulting b93-file was 140MB big.
But we know that most of the array will never be accessed,
only the columns between d/3 and d/2 are important and the biggest range is in the last row (LIMIT/3 - LIMIT/2).
So in each array-acess we modulo the x coordinate by LIMIT/3 - LIMIT/2 (= 2000).
Now our array has only a size of 12000x2000 and the befunge-file is only 23MB big.
The program is not that fast, but that's mostly because of it's raw size, the algorithm is quite good (200ms when I implement it in C#)