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

Terms

a(0) =-1a(1) =0a(2) =0a(3) =1a(4) =3a(5) =6a(6) =13a(7) =23a(8) =44a(9) =75a(10) =135a(11) =226a(12) =393a(13) =651a(14) =1108a(15) =1823a(16) =3059a(17) =5010a(18) =8325a(19) =13591a(20) =22428a(21) =36531a(22) =59983a(23) =97538a(24) =159569a(25) =259155a(26) =422820a(27) =686071a(28) =1117083a(29) =1811346