Recursive calculation means: Recursive equation is a mathematical expression, which refers to a series of equations with the same form but different parameters. Each equation can be obtained by simply recursing some parameters in the previous equation. In recursive equations, it is often seen that the parameters in the latter equation are some operation results of the parameters in the former equation. The calculation of recursive equation usually refers to the calculation of the value of the next parameter through recursive formula when the first few parameters are known, and then the law of sequence is obtained. In practical problems, recursive equations are usually used to derive mathematical models, describe mathematical relationships and calculate the related values in these relationships. The calculation of recursive equations is widely used in many mathematical fields, such as combinatorial mathematics, recursive theory, discrete mathematics and so on. For example, Fibonacci sequence is a very famous recursive equation, in which each term is obtained by adding the first two terms.