G.f. A(x) satisfies: A(x) = x + A( A(x)^2 + A(x)^4 ).

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =26a(5) =102a(6) =420a(7) =1793a(8) =7854a(9) =35106a(10) =159492a(11) =734334a(12) =3418892a(13) =16068532a(14) =76135112a(15) =363283763a(16) =1744135306a(17) =8419281306a(18) =40838500796a(19) =198950342814a(20) =972999755364