24407490807domain: NAppears in sequencesa(n) = 7*3^n.at n=20A005032a(n) = (7*3^n - 4*0^n)/3.at n=21A082541a(n) = (8*9^n + (-9)^n)/9.at n=11A083226a(n) = 3*a(n-1) for n>2; a(0)=1, a(1)=3, a(2)=7.at n=22A141495Expansion of g.f. (1-2*x)/(1-9*x).at n=11A270472a(n) = (n+1) * 3^(n-1).at n=19A288834