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

Terms

a(0) =1a(1) =0a(2) =-1a(3) =3a(4) =-6a(5) =6a(6) =15a(7) =-107a(8) =349a(9) =-672a(10) =39a(11) =5835a(12) =-27654a(13) =75765a(14) =-95799a(15) =-279129a(16) =2297970a(17) =-8377854a(18) =17663640a(19) =-996624a(20) =-177445221a(21) =888491025a(22) =-2551959604a(23) =3337931168a(24) =10407149226a(25) =-87719805853a(26) =328682535695a(27) =-708428979213a(28) =15252552804