47071589415domain: NAppears in sequencesNumber of vertices in Sierpiński triangle of order n.at n=22A067771a(n) = 3*a(n-1) + a(n-2) - 3*a(n-3).at n=23A103425a(0) = 2, a(n) = 3*a(n-1) - 3.at n=23A115098a(n) = 3*A132357(n).at n=21A135264a(n) = (3/2)*(1+(-3)^(n-1)).at n=23A165553