30801920domain: NAppears in sequencesa(n) = 6*a(n - 1) - 12*a(n - 2) + 8*a(n - 3) for n >= 5, a(0) = 1, a(1) = 7, a(2) = 24, a(3) = 70, a(4) = 193.at n=18A339254