The coefficient of $x ^ { 3 }$ in the expansion of $\left( 1 + 2 x + 3 x ^ { 2 } \right) ^ { 6 }$ is equal to twice the coefficient of $x ^ { 4 }$ in the expansion of $\left( 1 - a x ^ { 2 } \right) ^ { 5 }$.
Find all possible values of the constant $a$.
A $\pm 2 \sqrt { 2 }$
B $\pm \sqrt { 17 }$
C $\pm \sqrt { 34 }$
D $\pm 2 \sqrt { 17 }$
E There are no possible values of $a$.