A recursive process defines a sequence an=an−12a_n = a_{n-1}^2an=an−12 with a1=2a_1 = 2a1=2. What is the value of a4a_4a4?
24=162^4 = 1624=16
28=2562^8 = 25628=256
216=655362^{16} = 65536216=65536
224=655362^{2^4} = 65536224=65536