JEE Main 2025 — 7 April, Morning Shift — Question 43

For $n \geq 2$, let $S_{n}$ denote the set of all subsets of $\{1,2, \ldots, n\}$ with no two consecutive numbers. For example $\{1,3,5\} \in S_{6}$ but $\{1,2,4\} \notin S_{6}$. Then $n\left(S_{5}\right)$ is equal to $\_\_\_\_$ -.