FYI, I did a quick filter of the latest EDSM dumps for stations and populated systems, only looking at stations that are either "<something> Starport", "Outpost" or "Asteroid base", and only reporting systems which have 2 or more of those plus a population of not less than 2 million, and there appears to be 5831 systems which meet this criteria. Unfortunately, landing pad size is not in the station info to give precisely what you wanted (and since I think that would be really useful anyway, I've asked on the EDSM topic if it can be added).
Edit: Was just browsing about this and it seems that outposts can only handle up to medium size? On that basis, removing "Outpost" from the station criteria reduces the number of systems to a "mere" 1667.
Edit 2: Ok, went to EDDB and downloaded their stations and populated systems dumps, the former of which does include landing pad size. Filtered using the three "Starport" choices plus "Asteroid base", and the landing pad size of course, and this gives 1770 systems. You can have the list, here:
https://drive.google.com/open?id=1vCF2B7_GQlVisYFMpsPpZnSisWhG7ULh (the second value on each line is the number of large landing pads in that system). Do let me know if I've made a mistake.