Solution (source code)

= Solution

For $\operatorname{Re}p>0$, the starting integral is $\int_0^\infty e^{-pt}\,dt=1/p$. Repeated <integration by parts>, with vanishing boundary terms, gives
$$
\mathcal L[t^n](p)=\frac np\mathcal L[t^{n-1}](p)
=\boxed{\frac{n!}{p^{n+1}}}\qquad(n\ge0).
$$
This also follows from the <gamma function>. The stated open half-plane ensures absolute convergence.