Question: what is the numbers between 1 and 81 which are divisible by 4?
Answer: Expressing numbers divisible by 4 between 1 and 81 as an arithmetic sequence it will give: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, and 80.