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

Terms

a(0) =1a(1) =1a(2) =3a(3) =14a(4) =67a(5) =348a(6) =1898a(7) =10738a(8) =62439a(9) =370895a(10) =2241012a(11) =13730328a(12) =85103286a(13) =532673423a(14) =3362122902a(15) =21375465814a(16) =136763670651a(17) =879940122276