I can name the first 251(gen 1 and 2) by heart and 3 by sight and name, but not by number. It gets a little easier when you realize Gen2 is only 100 pokemon, the smallest Gen. Celebi is #251 and you can work backwards to Mew.
Easy way to solve most gens if you have to fill out a blank sheet - The starters are always grass/fire/water in that order, so your first 9 are always solved. Then the 2 early game bugs(Butterfree and Beedrill/ledyba and spinarak) and HM rat (Rattata/sentret/zigzagoon)and then from there’s it’s wild west until the end. The pseudo-legendary evo of 3 are with the legendaries, and those come in a set of 3, followed by the 2 title characters plus their hidden legendary so that’s the back 9 solved for most gens. Gen 4 has more legendaries/pseudo legendaries so you get 12-15 for free on the back end.
There’s some new ones I like but fuck there’s over 1000 now. I’m happy just knowing up to 386.