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) =15a(3) =40a(4) =97a(5) =238a(6) =575a(7) =1392a(8) =3361a(9) =8118a(10) =19599a(11) =47320a(12) =114241a(13) =275806a(14) =665855a(15) =1607520a(16) =3880897a(17) =9369318a(18) =22619535a(19) =54608392a(20) =131836321a(21) =318281038a(22) =768398399a(23) =1855077840a(24) =4478554081a(25) =10812186006a(26) =26102926095a(27) =63018038200a(28) =152139002497a(29) =367296043198