Binary reversal of 3^n.

Terms

a(0) =1a(1) =3a(2) =9a(3) =27a(4) =69a(5) =207a(6) =621a(7) =3345a(8) =4275a(9) =25497a(10) =38247a(11) =229173a(12) =589185a(13) =1669443a(14) =5205897a(15) =14045019a(16) =34319397a(17) =102566511a(18) =307313949a(19) =1843835217a(20) =2312645619a(21) =13776780249a(22) =20417442711a(23) =112792132341a(24) =290155405761a(25) =847524815523