Sum over all subsets of {1,..,n} of the GCD of the subset.

Terms

a(0) =1a(1) =4a(2) =10a(3) =22a(4) =42a(5) =84a(6) =154a(7) =298a(8) =568a(9) =1108a(10) =2142a(11) =4254a(12) =8362a(13) =16636a(14) =33076a(15) =66004a(16) =131556a(17) =262974a(18) =525136a(19) =1050016a(20) =2098756a(21) =4196962a(22) =8391288a(23) =16782312a(24) =33559612a(25) =67118176a(26) =134227594a(27) =268453714a(28) =536889198a(29) =1073777718