a(n) = -2*a(n-1)+4*a(n-2), n>1 ; a(0) = 1, a(1) = -4.

Terms

a(0) =1a(1) =-4a(2) =12a(3) =-40a(4) =128a(5) =-416a(6) =1344a(7) =-4352a(8) =14080a(9) =-45568a(10) =147456a(11) =-477184a(12) =1544192a(13) =-4997120a(14) =16171008a(15) =-52330496a(16) =169345024a(17) =-548012032a(18) =1773404160a(19) =-5738856448a(20) =18571329536a(21) =-60098084864a(22) =194481487872a(23) =-629355315200