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In order to create a larger set of file sizes with a larger median file size you could use stdnormal_rnd(1,500) * 256) + 512. This will create 500 file size entries between 1 and 1024.
Then save the generated vector into a file
octave:2> save "file_sizes.txt" x;
The data file needs some postprocessing (remove comments, insert line breaks). This can be achieved with some standard GNU tools:
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