208573domain: NAppears in sequencesa(n) = 2*a(n-1) + a(n-2) - 4*a(n-3) + 2*a(n-4) + a(n-5) -2*a(n-6) + a(n-7) for n >= 7, a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 11, a(4) = 18, a(5) = 30, a(6) = 47.at n=26A289077