Sequence basics

A sequence is an ordered list of numbers called terms: a₁, a₂, a₃, … A rule tells how to find any term, either from n directly or from the term before.

a₁, a₂, a₃, …Sequence basics

📐 Formula

aₙ = the n-th term

✏️ Worked example

3, 7, 11, 15, 19, 23, …: each term adds 4, and the 6th term is 23.

🌍 Where it is used

Patterns in tiles, savings each month, seats in rows of a stadium.

❓ Quick check

Next term of 5, 10, 15, 20, …?

🏋️ Practice

EasyNext term: 2, 4, 8, 16, …

Answer: 32

MediumNext term: 1, 4, 9, 16, …

Answer: 25

ChallengeWrite the first 4 terms of aₙ = 3n − 1.

Answer: 2, 5, 8, 11