64570080domain: NAppears in sequencesa(n) = (3^n - 3)/2.at n=16A029858a(n) = 3*(a(n-2) + 1), with a(0) = 1, a(1) = 3.at n=31A087503Expansion of (1+3x)/((1-x^2)(1-3x^2)).at n=31A094025a(n) = 6 * A015518(n).at n=16A120471a(0) = 1, a(1) = 3, a(n) = 3*a(n-1) + 3 for n > 1.at n=16A123109