4n - 1 Find the difference between the numbers and this decides the number infront of n In the sequence, choose 1 to start - 4n - if n = 4 then this gives you 4 but we need 3 so 4n-1 If we test this and put in the second number in the sequence we have 4x2 =8 but we need 7 so subtract 1. Therefore, this is correct