Let [x] denote greatest integer less than or equal to x. If for n ∈ N, (1-x+x^3)^n =Σ_j=0^3 n a_j x^j, then Σ_j=0^[(3 n)/2] a_2 j+4 Σ_j=0^[(3 n-1)/2]…

Let $\displaystyle [x]$ denote greatest integer less than or equal to $\displaystyle x$. If for $\displaystyle \mathrm{n} \in \mathrm{N}$, $\displaystyle \left(1-x+x^3\right)^{\mathrm{n}}=\sum_{j=0}^{3 \mathrm{n}} \mathrm{a}_j x^j$, then $$\sum_{j=0}^{\left[\frac{3 n}{2}\right]} a_{2 j}+4 \sum_{j=0}^{\left[\frac{3 n-1}{2}\right]} a_{2 j+1} \text { is equal to : } $$