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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =17a(5) =52a(6) =168a(7) =561a(8) =1922a(9) =6719a(10) =23871a(11) =85938a(12) =312823a(13) =1149421a(14) =4257460a(15) =15880036a(16) =59594517a(17) =224856450a(18) =852491806a(19) =3245959002a(20) =12407332166a(21) =47592364107a(22) =183139542306a(23) =706794663136