A number sequence is a list of numbers that are orders of numbers that are linked by a rule.

The numbers 3, 6, 9 are an example of an arithmetic sequence. The difference between each number is 3. So the rule for this sequence is to add 3 each time. Now you can find the next number in the sequence: 9 + 3 = 12. So the fourth number is 12.

a_n - the n^th term in the sequence

a₁ - the first term in the sequence

d - the common difference between terms

S_n - The sum of the arithmetic sequence

The numbers 6, 12, 24 are an example of an geometric sequence. The ratio between each number is 2. So the rule for this sequence is to multiply 2 each time. Now you can find the next number in the sequence: 24 * 2 = 48. So the fourth number is 48.

b_n - the n^th term in the sequence

b₁ - the first term in the sequence

q - the common ratio between terms

S_n - The sum of the geometric sequence

Fibonacci Sequence is a series of numbers in which each number is the sum of the two preceding numbers. First 6 terms of Fibonacci sequence: 1, 1, 2, 3, 5, 8, ...