General rule of 3,5,7,9 Answer: The terms in the sequence are said to increase by a common difference, d. For example: 3, 5, 7, 9, 11, is an arithmetic progression where d = 2. The nth term of this sequence is 2n + 1 . In general, the nth term of an arithmetic progression, with first term a and common difference d, is: a + (n - 1)d . Step-by-step explanation: d = 2. d. For example: 3, 5, 7, 9, 11, 2n + 1 d, is: a + (n - 1)d .