2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/68749We consider a multiple arithmetical sum involving the Moebius function which despite its elementary appearance is in fact of a highly intriguing nature. We establish an asymptotic formula for the quadruple case that raises the first genuinely non-trivial situation. This is a rework of an old unpublished note of ours.8 pages/ver.2Number Theory11A25 (Primary); 11M06 (Secondary)text