2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/69880A binomial coefficient identity due to Zhi-Wei Sun is the subject of half a dozen recent papers that prove it by various analytic techniques and establish a generalization. Here we give a simple proof that uses weight-reversing involutions on suitable configurations involving dominos and colorings. With somewhat more work, the method extends to the generalization also.Latex, 7 pagesCombinatoricsAMS Classification Numbers: 05A19text