16, 8, 4, generalize the pattern by finding the nth term, beginning with n = 1. \

an = 16 * r^(n -1)  This is the rule.
Proof:

a1 = 16 * (1/2) ^(1-1)
a1 = 16* (1/2) ^ 0
a1 = 16

a2 = 16 * (1/2)^(2 - 1)
a2 = 16 *(1/2)^1
a2 = 16 * (1/2)
a2 = 8

a3 = 16 *(1/2)^(3 - 1)
a3 = 16 * (1/2)^2
a3 = 16 * (1/4)
a3 = 4

a4 = 16 * (1/2)^(4 - 1)
a4 = 16 * (1/2)^3
a4 = 16 * (1/8)
a4 = 2