G.f. A(x) satisfies: A(x)^2 = A( x^2*(1+x)/(1-x) ), with A(0) = 0.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =9a(7) =18a(8) =38a(9) =80a(10) =166a(11) =342a(12) =705a(13) =1463a(14) =3065a(15) =6492a(16) =13917a(17) =30217a(18) =66455a(19) =147920a(20) =332700a(21) =754544a(22) =1721596a(23) =3943344a(24) =9051155a(25) =20789895a(26) =47741587a(27) =109543782a(28) =251076670a(29) =574820868