G.f. A(x) satisfies A(x) = 1 + x*A(x)^3 / (1 + x*A(x)^3).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =-1a(6) =-58a(7) =-304a(8) =-1090a(9) =-2876a(10) =-4216a(11) =9244a(12) =106746a(13) =529962a(14) =1874628a(15) =4669760a(16) =4309742a(17) =-35179252a(18) =-277928680a(19) =-1269921008a(20) =-4214431912a(21) =-9197175241a(22) =30113526a(23) =128659598896a(24) =822227670866