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

Terms

a(0) =1a(1) =0a(2) =3a(3) =3a(4) =12a(5) =21a(6) =57a(7) =120a(8) =291a(9) =651a(10) =1524a(11) =3477a(12) =8049a(13) =18480a(14) =42627a(15) =98067a(16) =225948a(17) =520149a(18) =1197993a(19) =2758440a(20) =6352419a(21) =14627739a(22) =33684996a(23) =77568213a(24) =178623201a(25) =411327840a(26) =947197443a(27) =2181180963a(28) =5022773292a(29) =11566316181