Sequence has an important position and practicability in mathematics. Sequence is a special function, and its domain generally refers to a non-negative positive integer, sometimes it can also be a natural number, perhaps an infinite subset of natural numbers. Natural numbers are discrete, and sequences are usually called discrete functions, which are relative to functions whose domain is real numbers or real number intervals. As a discrete function, sequence plays an important role in mathematics.

Sequence has a wide range of applications in mathematics. For example, the calculation of the total number of stacked items needs to use the first n items and formulas of the series; Some problems in product specification design should use the principle of geometric series; The calculation of savings installment also needs some knowledge of series. In addition, the sequence also plays the role of connecting the past with the future. Many knowledge points of junior high school mathematics are based on the knowledge of junior high school series, such as quadratic function, trigonometric function, plane geometry and so on.