a(n) = A255458(2^n-1).

Terms

a(0) =1a(1) =5a(2) =25a(3) =101a(4) =361a(5) =1205a(6) =3865a(7) =12101a(8) =37321a(9) =114005a(10) =346105a(11) =1046501a(12) =3155881a(13) =9500405a(14) =28566745a(15) =85831301a(16) =257756041a(17) =773792405a(18) =2322425785a(19) =6969374501a(20) =20912317801a(21) =62745342005a(22) =188252803225a(23) =564791964101