a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3) - 2*a(n - 4) + a(n - 5).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =-1a(6) =-3a(7) =-1a(8) =3a(9) =5a(10) =3a(11) =-5a(12) =-13a(13) =-7a(14) =13a(15) =27a(16) =15a(17) =-25a(18) =-61a(19) =-37a(20) =57a(21) =135a(22) =81a(23) =-119a(24) =-297a(25) =-191a(26) =257a(27) =661a(28) =431a(29) =-549