Expansion of (1-3x+x^2)/((1+x^2)(1-4x+x^2)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =14a(4) =53a(5) =195a(6) =727a(7) =2716a(8) =10137a(9) =37829a(10) =141179a(11) =526890a(12) =1966381a(13) =7338631a(14) =27388143a(15) =102213944a(16) =381467633a(17) =1423656585a(18) =5313158707a(19) =19828978246a(20) =74002754277a(21) =276182038859