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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =7a(7) =12a(8) =19a(9) =33a(10) =59a(11) =102a(12) =181a(13) =329a(14) =593a(15) =1076a(16) =1979a(17) =3643a(18) =6723a(19) =12494a(20) =23289a(21) =43498a(22) =81557a(23) =153356a(24) =288925a(25) =545687a(26) =1032997a(27) =1958978a(28) =3721819a(29) =7083716