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

Terms

a(0) =1a(1) =3a(2) =6a(3) =24a(4) =96a(5) =396a(6) =1728a(7) =7839a(8) =36438a(9) =172680a(10) =831624a(11) =4058202a(12) =20021268a(13) =99697188a(14) =500429016a(15) =2529375300a(16) =12862429920a(17) =65760468840a(18) =337817930184