I noticed that there's really only a 4x4 square in the multiplication tables (6-9) that aren't obvious, and since the table itself is mirrored along the diagona

I noticed that there's really only a 4x4 square in the multiplication tables (6-9) that aren't obvious, and since the table itself is mirrored along the diagonal, there are only really 9 entries you truly need to memorize: 6x6, 6x7, 6x8, 6x9, 7x7, 7x8, 7x9, 8x8 and 8x9.