The subsequence A253065(2^n-1).

Terms

a(0) =1a(1) =5a(2) =17a(3) =65a(4) =229a(5) =813a(6) =2945a(7) =10513a(8) =37701a(9) =135261a(10) =484609a(11) =1737665a(12) =6229413a(13) =22330829a(14) =80057281a(15) =286996657a(16) =1028861637a(17) =3688409853a(18) =13222664897a(19) =47402353633a(20) =169934149285a(21) =609201913325