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

Terms

a(0) =-1a(1) =-1a(2) =-1a(3) =1a(4) =2a(5) =9a(6) =15a(7) =36a(8) =59a(9) =119a(10) =194a(11) =361a(12) =587a(13) =1044a(14) =1695a(15) =2931a(16) =4754a(17) =8069a(18) =13079a(19) =21916a(20) =35507a(21) =58959a(22) =95490a(23) =157521a(24) =255059a(25) =418724a(26) =677879a(27) =1108891a(28) =1794962a(29) =2928429