A Sequence is a set of things (usually numbers) that are in order.

A Sequence is a set of things (usually numbers) that are in order. Each number in the sequence is called a term (or sometimes "element" or "member")

In an Arithmetic Sequence the difference between one term and the next is a constant.

In other words, we just add the same value each time infinitely.

1,4,7,10,13,16,...

In general we could write an arithmetic sequence like this:

{a, a+d, a+2d, a+3d, ... }

where:

• a is the first term, and 
• d is the difference between the terms (called the "common difference")

Rule

We can write an Arithmetic Sequence as a rule:

n = a + d(n−1)