His latest, “÷ (Divide),” is the next in his mathematical operator series. In it Sheeran takes his folky six-string roots and adds in pop influence. “Eraser,” a bland Twenty One Pilots-like that features Sheeran rapping over a set of looped acoustic guitars. The track’s production feels more trendy than innovative. In a year’s time it’ll just feel stale. “Shape of You,” a tropical beat