By Shalosh B. Ekhad and Doron Zeilberger
(Exclusively published in the Personal Journal of Shalosh B. Ekhad and Doron Zeilberger and arxiv.org)
Written: Nov. 11, 2020
Yesterday we got an email from Victor S. Miller (CCR, Princeton) pointing our attention to this beautiful paper, and he commented that a certain lemma there can probably be done by so-called Wilf-Zeilberger proof theory. It turns out that Gosper suffices. This is the first proof in this note. But with all due respect to automatic proofs, sometimes it is nice to have a human touch, hence the second proof.