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

Terms

a(0) =1a(1) =1a(2) =3a(3) =-3a(4) =-1a(5) =3a(6) =3a(7) =-1a(8) =1a(9) =7a(10) =9a(11) =9a(12) =17a(13) =33a(14) =51a(15) =77a(16) =127a(17) =211a(18) =339a(19) =543a(20) =881a(21) =1431a(22) =2313a(23) =3737a(24) =6049a(25) =9793a(26) =15843a(27) =25629a(28) =41471a(29) =67107