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

Terms

a(0) =1a(1) =2a(2) =-2a(3) =6a(4) =-22a(5) =80a(6) =-228a(7) =18a(8) =6694a(9) =-65604a(10) =396804a(11) =-1336332a(12) =-2510244a(13) =64799884a(14) =-302351144a(15) =-1410221598a(16) =23754923526a(17) =16833211660