a(n) = a(n-1)^2 - a(n-2)^2.A001042a(n) = a(n-1)^2 - a(n-2)^2.Terms a(0) =1a(1) =2a(2) =3a(3) =5a(4) =16a(5) =231a(6) =53105a(7) =2820087664External referencesoeis: A001042