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

Terms

a(0) =1a(1) =2a(2) =5a(3) =22a(4) =94a(5) =452a(6) =2253a(7) =11640a(8) =61732a(9) =333924a(10) =1836052a(11) =10229434a(12) =57628078a(13) =327711260a(14) =1878658490a(15) =10845298128a(16) =62993496588a(17) =367874945560