Expansion of (1 +4*x -x^2)/((1-x^2)*(1-2*x-x^2)); a Pellian-related sequence.

Terms

a(0) =1a(1) =6a(2) =13a(3) =36a(4) =85a(5) =210a(6) =505a(7) =1224a(8) =2953a(9) =7134a(10) =17221a(11) =41580a(12) =100381a(13) =242346a(14) =585073a(15) =1412496a(16) =3410065a(17) =8232630a(18) =19875325a(19) =47983284a(20) =115841893a(21) =279667074a(22) =675176041a(23) =1630019160a(24) =3935214361a(25) =9500447886a(26) =22936110133a(27) =55372668156a(28) =133681446445a(29) =322735561050