2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/226978We prove that certain numbers occurring in a problem of paths enumeration, studied by Niederhausen (Catlan Traffic at the Beach, The Electronic Journal of Combinatorics, 9, (2002), 1--17), are top intersection numbers in the cohomology ring of the grassmannians of the lines in the complex projective (n+1)-space.Excerpt from my Ph.D. Thesis; to appear on "Discrete Mathematics"Algebraic Geometry14M15;05C35text