If you mean to say that those numbers are a part of a sequence that you want to know how to complete then the pattern seems to be to divide the first term by 2 to get the next term and then multiply that term by 3 to get the term after it. So 120 divided by 2 is 60, 60 times 3 is 180, 180 divided by 2 is 90, 90 times 3 is 270 and 270 divided by 2 is 135.
