## Sequence

A sequence is a collection of numbers and terms.Sequence may be finite and infinite.

## Finite sequence :

$$\{a_1,a_2,a_3,a_4,a_5\}$$

## Infinite sequence :

$$\{a_1,a_2,a_3,a_4,......a_n\}$$

## Arithmetic sequence

A pattern of terms or numbers that increase or decrease at a constant amount.

**Example:**

$$\{1,5,9,13,17,21,25,29,33\}$$

This sequence has a difference of 4 between each number.

We could write like that:

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

**a** is the first term, and

**d** is the difference between them.

Now

$$a = 1$$

$$d = 4$$

So,

$$\{1,1+4,1+2*4,1+3*4,1+4*4,1+5*4……….\}$$

$$\{1,5,9,13,17,21……….\}$$