What are the rules of 2.8,4,5.6,8,11,16,22

What are the rules of 2.8,4,5.6,8,11,16,22


The rule of the first, third, fifth and seventh digits is: 2.8, 2.8 * 2 = 5.6, 5.6 * 2 = 11, 11 * 2 = 22. The first digit is twice of the last digit, and the last digit is twice of the last digit