An arithmetic sequence is a list of numbers in which each term after the first is found by adding a constant value, known as the common difference, to the previous term. For example, in the sequence 2, 5, 8, 11, the common difference is 3, as each number increases by 3. Arithmetic sequences can be represented using a formula: a_n = a_1 + (n-1) \cdot d , where a_n is the nth term, a_1 is the first term, n is the term number, and d is the common difference. These sequences are widely used in various fields, including mathematics and finance.