$$\begin{aligned} \left\vert a_{n}\right\vert &\leq &\frac{\prod\limits_{k=0}^{n}\left[ k-0+\frac{0\left( \beta -\delta \right) }{\pi }\sin \frac{\pi \left( 0-\delta \right) }{\beta -\delta }\right] }{n!} \\ &&+\frac{