An integer sequence is a sequence (i.e. an infinite list) of integers.
An integer sequence may be specified explicitly by giving a formula for its n-th term, or implicitly by giving a relationship between its terms. For example, the sequence 1, 1, 2, 3, 5, 8, 13, ... (the Fibonacci sequence) is formed by starting with two ones and then adding any two consecutive terms to obtain the next one: an implicit description. The sequence 0, 3, 8, 15, ... is formed according to the formula n2 - 1 for the n-th term: an explicit definition.