Expansion of g.f.: (1+3*x^2)/((1-x)*(1+x+2*x^2)*(1-x+2*x^2)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =-3a(5) =-3a(6) =9a(7) =9a(8) =-11a(9) =-11a(10) =1a(11) =1a(12) =45a(13) =45a(14) =-135a(15) =-135a(16) =229a(17) =229a(18) =-143a(19) =-143a(20) =-483a(21) =-483a(22) =2025a(23) =2025a(24) =-4139a(25) =-4139a(26) =4321a(27) =4321a(28) =3597a(29) =3597