Coefficient of x^n in the expansion of ( (1-x+x^3) / (1-x) )^n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =3a(4) =4a(5) =5a(6) =21a(7) =49a(8) =92a(9) =237a(10) =595a(11) =1331a(12) =3169a(13) =7787a(14) =18487a(15) =44108a(16) =107036a(17) =258349a(18) =622371a(19) =1508239a(20) =3658679a(21) =8869465a(22) =21543005a(23) =52399612a(24) =127497281a(25) =310487855a(26) =756858661a(27) =1846060464a(28) =4505442967a(29) =11003284052