Expansion of g.f.: (1+x)/(1-8*x).

Terms

a(0) =1a(1) =9a(2) =72a(3) =576a(4) =4608a(5) =36864a(6) =294912a(7) =2359296a(8) =18874368a(9) =150994944a(10) =1207959552a(11) =9663676416a(12) =77309411328a(13) =618475290624