Coefficient of x^n in the expansion of ( (1+x+x^3)^3 / (1+x)^2 )^n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =10a(4) =37a(5) =91a(6) =334a(7) =1366a(8) =4645a(9) =15967a(10) =59951a(11) =220782a(12) =792946a(13) =2906554a(14) =10770082a(15) =39629440a(16) =145966549a(17) =540943231a(18) =2006762563a(19) =7443051014a(20) =27661527427a(21) =102980882455a(22) =383639407570