Expansion of (1 +3*x -x^2)/((1-x^2)*(1-2*x-x^2)); a Pellian-related sequence.

Terms

a(0) =1a(1) =5a(2) =11a(3) =30a(4) =71a(5) =175a(6) =421a(7) =1020a(8) =2461a(9) =5945a(10) =14351a(11) =34650a(12) =83651a(13) =201955a(14) =487561a(15) =1177080a(16) =2841721a(17) =6860525a(18) =16562771a(19) =39986070a(20) =96534911a(21) =233055895a(22) =562646701a(23) =1358349300a(24) =3279345301a(25) =7917039905a(26) =19113425111a(27) =46143890130a(28) =111401205371a(29) =268946300875