G.f.: real part of 1/(1 - i*x - i*x^2) where i=sqrt(-1).

Terms

a(0) =1a(1) =0a(2) =-1a(3) =-2a(4) =0a(5) =4a(6) =5a(7) =-2a(8) =-13a(9) =-12a(10) =12a(11) =40a(12) =25a(13) =-52a(14) =-117a(15) =-38a(16) =196a(17) =324a(18) =-3a(19) =-678a(20) =-841a(21) =360a(22) =2200a(23) =2000a(24) =-2079a(25) =-6760a(26) =-4121a(27) =8918a(28) =19720a(29) =6084