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

Terms

a(0) =0a(1) =3a(2) =9a(3) =26a(4) =78a(5) =234a(6) =702a(7) =2106a(8) =6318a(9) =18954a(10) =56862a(11) =170586a(12) =511758a(13) =1535274a(14) =4605822a(15) =13817466a(16) =41452398a(17) =124357194a(18) =373071582a(19) =1119214746a(20) =3357644238a(21) =10072932714a(22) =30218798142a(23) =90656394426a(24) =271969183278a(25) =815907549834