[tex]4 , 27 , 256 , ? \\ \\ [/tex]

[tex]4 = {2}^{2} \\ \\ 27 = {3}^{3} \\ \\ 256 = {4}^{4} [/tex]

So, we have a pattern.

Next term is

[tex] {5}^{5} = 3125 \\ \\ [/tex]

Hence, the series is

[tex]4 , \: 27 , \: 256 , \: 3125 \\ [/tex]