An arithmetic progression or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. For instance, the sequence 5, 7, 9, 11, 13, 15.. . is an arithmetic progression with a common difference of 2.Which is an arithmetic sequence? An arithmetic sequence (also known as an arithmetic progression) is a sequence of numbers in which the difference between consecutive terms is always the same. For example, in the arithmetic sequence 1, 5, 9, 13, 17, …, the difference is always 4. This is called the common difference.