Are they random or are there hidden mechanics like trainer ID, gender, day, ball, third number for your pokedollars, current time translated from your time to france time in metric, etc? Asking because

Leaf Green
Trying to catch a Sp Atk up Seel. after about 50 attempts and nothing. Finding a lot of Atk Up Seels, but. My Beedrill and Farfetch'd were Adamant right off the bat, and only two or three Mankeys for an Adamant one and my Butterfree took about 10 catches to find a Sp Atk up version.