The equation a_n = a_n-1 describes a sequence where each term is equal to the previous term. This means that the value of each term does not change as you progress through the sequence. For example, if the first term a_1 is 5, then every subsequent term will also be 5, resulting in a constant sequence like 5, 5, 5, .... This type of sequence is known as a constant sequence. It is a simple mathematical concept often used in introductory algebra to illustrate the idea of sequences and series. Understanding this concept lays the groundwork for more complex sequences and mathematical patterns.