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

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =51a(5) =266a(6) =1540a(7) =9681a(8) =65291a(9) =468401a(10) =3551693a(11) =28327029a(12) =236731183a(13) =2066583601a(14) =18796448581a(15) =177735656083