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

Terms

a(0) =1a(1) =1a(2) =4a(3) =16a(4) =74a(5) =364a(6) =1876a(7) =9993a(8) =54582a(9) =304040a(10) =1720576a(11) =9864114a(12) =57169168a(13) =334404892a(14) =1971641096a(15) =11705119157a(16) =69911438676a(17) =419798442416