Hi, my son (13) was asked this question in school. If you have one germ and it doubles every 20 mins for 24 hours. how many germs will you have?

My idea is at 20 mins you would have 2 germs then at 40 mins you would have 4 germs then at 60 mins you would have 8 germs at 80 mins you would have 16 germs at 100 mins you would have 32 germs and so on...

Giving that 24 hours has 1440 mins then you would have to continue the string until you reach the 1440 mins

Am i right or wrong? if im wrong how do i figure it out?