The term "a_n" typically represents the n-th term in a sequence or series in mathematics. It is often used in contexts such as arithmetic sequences, geometric sequences, or other mathematical constructs where each term is defined based on its position, n. For example, in an arithmetic sequence, a_n can be expressed as a_n = a_1 + (n-1)d, where a_1 is the first term and d is the common difference. In more advanced mathematics, "a_n" can also denote terms in a function or a polynomial. It is a convenient notation that helps simplify expressions and calculations, especially when dealing with infinite series or recursive sequences. Understanding "a_n" is essential for studying topics like calculus, number theory, and combinatorics.