What is the missing term? pllus,+4 4, x4x question mark? 2, x2x 2, x, squared2x 2 4, x4x xx plus, 2+2

The missing term is 16.

The sequence is as follows:
pllus, +4
4, x4x
question mark
2, x2x
2, x, squared
2x
2
4, x4x
xx plus, 2+2

So, pllus = 4 + 4 = 8
4, x4x = 4 x 4 x 4 = 64
2, x2x = 2 x 2 x 2 = 8
2, x, squared = 2^2 = 4
2x = 2 x 2 = 4
4, x4x = 4 x 4 x 4 = 64
xx plus, 2+2 = 2 + 2 = 4

Therefore, the missing term is 16.