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

Terms

a(0) =0a(1) =1a(2) =4a(3) =7a(4) =16a(5) =21a(6) =52a(7) =71a(8) =160a(9) =277a(10) =564a(11) =1035a(12) =2176a(13) =4109a(14) =8348a(15) =16467a(16) =33088a(17) =65553a(18) =131740a(19) =262163a(20) =525456a(21) =1048817a(22) =2099244a(23) =4194327a(24) =8393344a(25) =16777321a(26) =33562676a(27) =67109695a(28) =134234480a(29) =268435485