For example if \( n = 6 \) :
\[\begin{aligned} t(n) &= t(n) \cdot t(n-1) \cdot t(n-2) \cdot t(n-3) \cdot t(n-4) \cdot t(n-5) \\ &= \underbrace{6 \cdot 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1}_{\text{this happens } n \text{ times}} \end{aligned}\]So we have a time complexity of \( O(n) \) .
