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

Terms

a(0) =1a(1) =3a(2) =12a(3) =61a(4) =345a(5) =2085a(6) =13182a(7) =86106a(8) =576543a(9) =3936029a(10) =27294390a(11) =191722887a(12) =1361291244a(13) =9754412169a(14) =70447946556a(15) =512278417176