423644304723domain: NAppears in sequencesNumber of vertices in Sierpiński triangle of order n.at n=24A067771a(n) = 3*a(n-1) + a(n-2) - 3*a(n-3).at n=25A103425a(0) = 2, a(n) = 3*a(n-1) - 3.at n=25A115098