We can see in the sequence is :
[tex]0,3,8[/tex]That is a squar of side 1 minus one square so the solution will be:
[tex]n^2-1[/tex]and we can replace the first 3 steps to be sure of the answe so:
[tex]\begin{gathered} 1\to1^2-1=0 \\ 2\to2^2-1=3 \\ 3\to3^2-1=8 \end{gathered}[/tex]