When you select Scan QR Code from your in-game menu, you can register Pokémon as Seen in your Pokédex.
Players can go to their registered Pokédex Entries, to share QR codes for other players to scan.
These codes were generated so that players can have them Seen in their Pokédex.
Can be useful for finding their habitats in the dex (if they are in the dex), or having them show up in GTS search function without having to type it's name.
Credits to SciresM for generating them.