\begin{array} & &2 &1 &3 \\\ &1 &3 &2 \\\ &3 &2 &1 \\\ \end{array}
This cannot represent a group because there is no identity element. $1*1=2$, $2*2=3$, and $3*3=1$.
\begin{array} & &2 &1 &3 \\\ &1 &3 &2 \\\ &3 &2 &1 \\\ \end{array}
This cannot represent a group because there is no identity element. $1*1=2$, $2*2=3$, and $3*3=1$.