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

Terms

a(0) =1a(1) =3a(2) =11a(3) =53a(4) =284a(5) =1630a(6) =9794a(7) =60830a(8) =387390a(9) =2515892a(10) =16599051a(11) =110943779a(12) =749603067a(13) =5111606801a(14) =35133394554a(15) =243146923574