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) = 2, a(3) = 1.

Terms

a(0) =0a(1) =0a(2) =2a(3) =1a(4) =7a(5) =6a(6) =21a(7) =23a(8) =60a(9) =75a(10) =167a(11) =226a(12) =457a(13) =651a(14) =1236a(15) =1823a(16) =3315a(17) =5010a(18) =8837a(19) =13591a(20) =23452a(21) =36531a(22) =62031a(23) =97538a(24) =163665a(25) =259155a(26) =431012a(27) =686071a(28) =1133467a(29) =1811346