a(n) = Sum_{d|n} 2^(d-1) * d^(n/d-1).

Terms

a(0) =1a(1) =3a(2) =5a(3) =13a(4) =17a(5) =53a(6) =65a(7) =177a(8) =293a(9) =625a(10) =1025a(11) =2541a(12) =4097a(13) =8769a(14) =17109a(15) =34561a(16) =65537a(17) =136013a(18) =262145a(19) =534481a(20) =1054629a(21) =2110465a(22) =4194305a(23) =8449325a(24) =16787217a(25) =33615873a(26) =67155845a(27) =134403521a(28) =268435457a(29) =537370845