Sequences are ordered element lists, which are used in many respects in discrete mathematics. They can, for example, be used to solve certain counting problems. They are also a key computer science data structure.The sequence terms can be specified with a formula for each sequence term.

## Definition

A sequence is a discrete structure used to represent an ordered list.

**For Example:**

1,2,3,6,8 is a sequence with five terms and 1, 3, 9, 27, 81 , . . . , 3n, . . . is an infinite sequence.

A Sequence can also be defined as a function whose domain is either the set of the natural numbers (for infinite sequences) or the set of the first

We use the notation an to denote the image of the integer n.nnatural numbers (for a sequence of finite lengthn). [Wikipedia]

We call an a term of the sequence.