$$\left. \begin{array} { l } { 2 , 12 , 22 , 32 , - 1 } \\ { - 2 \quad a _ { n } = \frac { 3 } { 2 n + 1 } } \end{array} \right.$$
$-2a_{n}=\frac{3}{2n+1},\ a=2,\ b=12,\ c=22,\ d=32,\ \text{false}$
