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

Terms

a(0) =0a(1) =1a(2) =-1a(3) =0a(4) =0a(5) =2a(6) =-3a(7) =1a(8) =0a(9) =4a(10) =-8a(11) =5a(12) =-1a(13) =8a(14) =-20a(15) =18a(16) =-7a(17) =17a(18) =-48a(19) =56a(20) =-32a(21) =41a(22) =-113a(23) =160a(24) =-120a(25) =114a(26) =-267a(27) =433a(28) =-400a(29) =348