There are many types of sequences:

Arithmetic sequences:   2, 8, 14, 20, 26, etc.    A constant is added.

Geometric sequences:    3, 9, 27, 81, etc.   A constant multiplies, in this case the number 3.

Fibonacci sequence:    1, 1, 2, 3, 5, 8, 13, etc., where every next term is the sum of the two previous terms.

Dual sequences:    2, 3, 8, 9, 14, 27, 20, 81, etc.  In this case it is a compilation of the two first sequences shown above alternating.

Triangular number sequence:   1, 3, 6, 10, 15, 21, 28, 36, etc.   We add 2 to 1, then 3, then 4, then 5.  The differences increase by 1.

Square number sequence:    1, 4, 9, 16, 25, 36, 49, etc.  Each number is a counting number squared.  1² = 1. 2² = 4   3²=9, etc.