Expansion of 1/sqrt(1-6x-3x^2).

Terms

a(0) =1a(1) =3a(2) =15a(3) =81a(4) =459a(5) =2673a(6) =15849a(7) =95175a(8) =576963a(9) =3523257a(10) =21640365a(11) =133549155a(12) =827418645a(13) =5143397535a(14) =32063180535a(15) =200367960201