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

Terms

a(0) =0a(1) =-1a(2) =1a(3) =1a(4) =6a(5) =9a(6) =23a(7) =36a(8) =75a(9) =119a(10) =226a(11) =361a(12) =651a(13) =1044a(14) =1823a(15) =2931a(16) =5010a(17) =8069a(18) =13591a(19) =21916a(20) =36531a(21) =58959a(22) =97538a(23) =157521a(24) =259155a(25) =418724a(26) =686071a(27) =1108891a(28) =1811346a(29) =2928429