## Precalculus (6th Edition) Blitzer

A recursion formula gives the nth term of a sequence as a function of the previous term. For example: $a_n=3a_{n-1}+4$ Here, $a_1$ is the initial term and $a_n$ is the each term after the first. $3a_{n-1}+4$ defines the next term as 3 times the previous term plus $4$.