G.f. A(x) satisfies: A(x)^2 - 2*A(x)^3 = A(x^2).

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =34a(5) =131a(6) =544a(7) =2321a(8) =10219a(9) =45858a(10) =209422a(11) =969115a(12) =4536240a(13) =21435168a(14) =102120900a(15) =489966937a(16) =2365411849a(17) =11481936107a(18) =56005441585a(19) =274365808690