First appearance of 2^n in A281130.

Terms

a(0) =1a(1) =3a(2) =7a(3) =13a(4) =23a(5) =41a(6) =98a(7) =223a(8) =437a(9) =699a(10) =1213a(11) =2624a(12) =4674a(13) =11163a(14) =21300a(15) =40858a(16) =73977a(17) =148591a(18) =297394a(19) =567076a(20) =1100738a(21) =2243474a(22) =4340628a(23) =8726122a(24) =17397270a(25) =34701556a(26) =68372147a(27) =136254352a(28) =271069771a(29) =546613630