a(n) = 2*a(n-2) + 2*a(n-3).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =4a(5) =6a(6) =12a(7) =20a(8) =36a(9) =64a(10) =112a(11) =200a(12) =352a(13) =624a(14) =1104a(15) =1952a(16) =3456a(17) =6112a(18) =10816a(19) =19136a(20) =33856a(21) =59904a(22) =105984a(23) =187520a(24) =331776a(25) =587008a(26) =1038592a(27) =1837568a(28) =3251200a(29) =5752320