48225038404domain: NAppears in sequencesa(0)=0, a(1)=4; for n > 1, a(n) = 18*a(n-1) - a(n-2) + 8.at n=9A132584a(n) = - sin^2((2n-1)*arccos(sqrt n)) = sin^2((2n-1)*arcsin(sqrt n)) - 1.at n=5A173171