Sequence is a general notion of an Ordered one-dimensional structure. (Tables and Threes are usually 2-d structures, while graphs and molecules are 3-d structures).
The canonical example of a sequence is a
List which is considered as a linear structure made out of pairs.
Pair itself is an kind of an Ordered Sequence - it is a linear structure of exactly two elements with an explicit order. The ADT consists of
cons car cdr pair?. Logically, Pair is a specialized instance of more general (and more abstract) type of Sequence, which implies ordered linear structure.