Let \( [x] \) denote greatest integer less than or equal to \( x \). If for \( n \in \mathbb{N},\left(1-x+x^{3}\right)^{…

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

[JEE Main 2021, 16 Mar (Shift 1)]