S = 4
s = s * 2 (for k :=13 to 20 - параметр цикла)
k = 13 s = 4 * 2 = 8
k = 14 s = 8 * 2 = 16
k = 15 s = 16 * 2 = 32
k = 16 s = 32 * 2 = 64
k = 17 s = 64 * 2 = 128
k = 18 s = 128 * 2 = 256
k = 19 s = 256 * 2 = 512
k = 20 s = 512 * 2 = 1024
Ответ: 1024