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

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =49a(5) =238a(6) =1217a(7) =6458a(8) =35233a(9) =196387a(10) =1113514a(11) =6402245a(12) =37239365a(13) =218737598a(14) =1295635858a(15) =7730216950a(16) =46414422333a(17) =280246784987