Question 36
Let
$$
\begin{aligned} (1+x+x^2)^n &=a_0+a_1x\\ &\quad+a_2x^2+\cdots\\ &\quad+a_{2n}x^{2n} \end{aligned}
$$
be an identity in $x.$ If we let $s=a_0+a_2+a_4+\cdots+a_{2n},$ then $s$ equals:
$$
\begin{aligned} (1+x+x^2)^n &=a_0+a_1x\\ &\quad+a_2x^2+\cdots\\ &\quad+a_{2n}x^{2n} \end{aligned}
$$
be an identity in $x.$ If we let $s=a_0+a_2+a_4+\cdots+a_{2n},$ then $s$ equals: