To insert one arithmetic sequence between 8 and 32, we need to find the number that is equally spaced from both. First, we add the two numbers: 8 plus 32 equals 40. Then, we divide the sum by 2 to get the middle term, which is 40 divided by 2 equals 20. Therefore, the number we insert is 20. The final arithmetic sequence is 8, 20, 32.