In case anyone has this question in the future, I figured out a way:

Select the entire column and go to Data--text to columns--Delimited, and select the appropriate separators (in this case, commas and spaces). This will put each number in its own cell.

Use:
=IF(COUNTIF($A1:A1,A1)=1, A1,"")

Drag it over to the right as many columns as necessary, and then drag it down as many rows as necessary. Any duplicates will be blank.

Select all of them, copy, paste special, "values."

Use MCONCAT to combine them again and voila! :D