The value of ${3}^{3-\log _35}$ is

If $\log (1-x+x^2)={{a}}_1x+{{a}}_{2{}^{{}^{}}}{x}^2+{{{}{{a}}_3{x}^3+.\ldots.}}^{}$  then ${{a}}_3+{{a}}_6+{{a}}_9+.\ldots.$ is equal to