a(n) = Sum_{d|n, d odd} d*2^(n/d - 1), a(0)=0.

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =8a(5) =21a(6) =38a(7) =71a(8) =128a(9) =277a(10) =522a(11) =1035a(12) =2072a(13) =4109a(14) =8206a(15) =16467a(16) =32768a(17) =65553a(18) =131186a(19) =262163a(20) =524328a(21) =1048817a(22) =2097174a(23) =4194327a(24) =8388992a(25) =16777321a(26) =33554458a(27) =67109695a(28) =134217784a(29) =268435485