Question 856215
It has two patterns
2^2, 4^2, 8^2 which is not geometric
and
4, 4*4, 4*16 which is geometric,
Your ratio (r)  is 4
t1=4 n=8 r=4

Tn = t1 * r^(n - 1)

S=t1*(1 - r^n)/(1 - r)
S=4*(1 - 4^8)/(1 - 2)
S = 262140