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

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =5a(5) =9a(6) =18a(7) =31a(8) =57a(9) =96a(10) =169a(11) =281a(12) =482a(13) =795a(14) =1341a(15) =2200a(16) =3669a(17) =5997a(18) =9922a(19) =16175a(20) =26609a(21) =43296a(22) =70929a(23) =115249a(24) =188226a(25) =305523a(26) =497845a(27) =807464a(28) =1313501a(29) =2129157