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

Terms

a(0) =1a(1) =-1a(2) =0a(3) =0a(4) =1a(5) =3a(6) =11a(7) =47a(8) =253a(9) =1651a(10) =12610a(11) =109744a(12) =1069355a(13) =11520785a(14) =135906642a(15) =1741702304a(16) =24089599321a(17) =357592702647