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

Terms

a(0) =1a(1) =3a(2) =9a(3) =30a(4) =99a(5) =327a(6) =1080a(7) =3567a(8) =11781a(9) =38910a(10) =128511a(11) =424443a(12) =1401840a(13) =4629963a(14) =15291729a(15) =50505150a(16) =166807179a(17) =550926687a(18) =1819587240a(19) =6009688407a(20) =19848652461a(21) =65555645790a(22) =216515589831a(23) =715102415283