G.f. satisfies: A(x) = A(x^2 + 2*x^3)/(1-x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =14a(6) =26a(7) =50a(8) =104a(9) =184a(10) =342a(11) =674a(12) =1356a(13) =2788a(14) =5518a(15) =10826a(16) =21370a(17) =42026a(18) =83522a(19) =167026a(20) =332744a(21) =656000a(22) =1275546a(23) =2467078a(24) =4781642a(25) =9309626a(26) =18249534a(27) =36020326a(28) =71503892a(29) =142624604