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

Terms

a(0) =0a(1) =0a(2) =2a(3) =3a(4) =2a(5) =0a(6) =3a(7) =14a(8) =26a(9) =27a(10) =22a(11) =44a(12) =123a(13) =234a(14) =310a(15) =363a(16) =586a(17) =1224a(18) =2259a(19) =3382a(20) =4642a(21) =7227a(22) =13070a(23) =23092a(24) =36555a(25) =54450a(26) =85022a(27) =143883a(28) =245282a(29) =396720