G.f.: (1+x+x^2-sqrt(1+2x+3x^2-2x^3+x^4))/2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =-1a(5) =0a(6) =2a(7) =-4a(8) =3a(9) =5a(10) =-20a(11) =29a(12) =-1a(13) =-94a(14) =221a(15) =-191a(16) =-327a(17) =1454a(18) =-2282a(19) =162a(20) =8002a(21) =-19902a(22) =18275a(23) =30505a(24) =-143511a(25) =234364a(26) =-24437a(27) =-841723a(28) =2164873a(29) =-2069014