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

Terms

a(0) =1a(1) =1a(2) =0a(3) =-1a(4) =0a(5) =1a(6) =0a(7) =0a(8) =0a(9) =-1a(10) =0a(11) =1a(12) =0a(13) =0a(14) =0a(15) =-2a(16) =0a(17) =3a(18) =0a(19) =-1a(20) =0a(21) =-3a(22) =0a(23) =6a(24) =0a(25) =-4a(26) =0a(27) =-4a(28) =0a(29) =12