a(n) = A055086(2^n).

Terms

a(0) =2a(1) =3a(2) =4a(3) =7a(4) =10a(5) =15a(6) =21a(7) =31a(8) =44a(9) =63a(10) =89a(11) =127a(12) =180a(13) =255a(14) =361a(15) =511a(16) =723a(17) =1023a(18) =1447a(19) =2047a(20) =2895a(21) =4095a(22) =5791a(23) =8191a(24) =11584a(25) =16383a(26) =23169a(27) =32767a(28) =46339a(29) =65535