The document discusses arithmetic sequences and how to find missing or future terms in an arithmetic sequence using the formula an = a1 + (n - 1)d, where an is the nth term, a1 is the first term, n is the number number, and d is the common difference. It provides examples of arithmetic sequences and asks the reader to identify whether example sequences are arithmetic or not. It also gives illustrative examples of using the formula to find specific terms in arithmetic sequences.