Expansion of g.f. (1+4*x)/(1-8*x).

Terms

a(0) =1a(1) =12a(2) =96a(3) =768a(4) =6144a(5) =49152a(6) =393216a(7) =3145728a(8) =25165824a(9) =201326592a(10) =1610612736a(11) =12884901888a(12) =103079215104a(13) =824633720832