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

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =37a(6) =112a(7) =351a(8) =1130a(9) =3716a(10) =12424a(11) =42101a(12) =144277a(13) =499136a(14) =1740871a(15) =6114629a(16) =21609654a(17) =76786625a(18) =274171192a(19) =983187372a(20) =3539498904a(21) =12787269117a(22) =46345303727a(23) =168463177245a(24) =614002351108