The 64 hexagrams, two ways
The King Wen sequence
The order of the book: pairs, each hexagram beside its inverse or, where the figure is its own inverse, its opposite.
The Fuxi square
The order of the figures themselves, trigram by trigram.
Columns: the lower trigram, 乾 兌 離 震 巽 坎 艮 坤. Rows: the upper trigram in the same order. Neighbours differ by one line.