O.g.f. satisfies A(x/(1-x)) = 1/(1-x*A(x)-x^2*A(x)^2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =19a(6) =41a(7) =87a(8) =188a(9) =399a(10) =855a(11) =1839a(12) =3908a(13) =8300a(14) =18406a(15) =37287a(16) =78412a(17) =217444a(18) =208980a(19) =752447a(20) =6966312a(21) =-32965587a(22) =103369671a(23) =665090041a(24) =-9555165542a(25) =56572244738a(26) =-57544084949