From Bulbapedia, the community-driven Pokémon encyclopedia.
In each Pokémon game of Generation VII, all Pokémon have an unseen index number used to identify them in the game's ROM. All of them are in their National Pokédex order.
List of Pokémon by index number
|| This list is incomplete.|
Please feel free to edit this list to add missing information and complete it.
Reason: 803+ glitch Pokémon in Sun/Moon (see https://www.youtube.com/watch?v=VOpMfNEg1jE), 808+ in USUM, 152-807 and 810+ in Let's Go (only 151 + Meltan/Melmetal are programmed but slots exist for the left out Pokémon). Also, what occupies 000?.
Pokémon Sun, Moon, Ultra Sun, and Ultra Moon
Pokémon Ultra Sun and Ultra Moon
Pokémon Let's Go, Pikachu! and Let's Go, Eevee!