Expansion of g.f. (1+4*x)/(1-5*x).

Terms

a(0) =1a(1) =9a(2) =45a(3) =225a(4) =1125a(5) =5625a(6) =28125a(7) =140625a(8) =703125a(9) =3515625a(10) =17578125a(11) =87890625a(12) =439453125a(13) =2197265625a(14) =10986328125a(15) =54931640625a(16) =274658203125