a(n) = -4*a(n-1) - 3*a(n-2) + a(n-3), a(0) = 1, a(1) = -2, a(2) = 4.

Terms

a(0) =1a(1) =-2a(2) =4a(3) =-9a(4) =22a(5) =-57a(6) =153a(7) =-419a(8) =1160a(9) =-3230a(10) =9021a(11) =-25234a(12) =70643a(13) =-197849a(14) =554233a(15) =-1552742a(16) =4350420a(17) =-12189221a(18) =34152882a(19) =-95693445a(20) =268125913a(21) =-751270435a(22) =2105010556a(23) =-5898105006a(24) =16526117921a(25) =-46305146110a(26) =129744125671a(27) =-363534946433