A remark concerning sinc integrals

Abstract

We give a simple proof of Hanspeter Schmid's result that $K_n:=2\int_0^\infty\cos t\,\prod_{k=0}^n\mathrm{sinc}\left(\frac{t}{2k+1}\right)\mathrm{d}t=\pi/2$ if $n\in\{0,1,\ldots,55\}$, and $K_n<\pi/2$ if $n\geq 56$. Furthermore, we present two sinc integrals where the value $\pi/2$ is undercut as soon as $n\geq 418$ and $n\geq 3091$, respectively.