I always see an image that skips a lot of the missing combinations by putting the same Pokémon in two spaces. I know that for competitive play, when type weaknesses and resistances are applied there's no difference between Water/Bug or Bug/Water for example. However, design wise, I think there IS a difference (or all type combinations would always have the same order).
Why is Omanyte Rock/Water but Corsola is Water/Rock? I don't know, but it IS different, and thus most people think of Corsola as a Water Pokémon, before we think of Rock, and we think of Omanyte as a Rock Pokémon, before we think of it as Water.
So on this chart I did, the rows represent the primary type and the columns represent the secondary type. So we have Smoliv, a Grass/Normal Pokémon, and then we have Deerling, a Normal/Grass, and so on.
You see then, there's lots of missing combinations. or should I say permutations. And the worst part is that there's been a lot of chances to fill those spaces, but they keep repeating them instead.
by wwwHttpCom