a(n) = (-1)*a(n-1) + 3*a(n-2) with a(1)=-1 and a(2)=1.

Terms

a(0) =-1a(1) =1a(2) =-4a(3) =7a(4) =-19a(5) =40a(6) =-97a(7) =217a(8) =-508a(9) =1159a(10) =-2683a(11) =6160a(12) =-14209a(13) =32689a(14) =-75316a(15) =173383a(16) =-399331a(17) =919480a(18) =-2117473a(19) =4875913a(20) =-11228332a(21) =25856071a(22) =-59541067a(23) =137109280a(24) =-315732481a(25) =727060321a(26) =-1674257764a(27) =3855438727a(28) =-8878212019a(29) =20444528200