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

Terms

a(0) =2a(1) =12a(2) =20a(3) =56a(4) =52a(5) =168a(6) =156a(7) =432a(8) =614a(9) =1272a(10) =2092a(11) =4784a(12) =8244a(13) =17064a(14) =33160a(15) =67040a(16) =131140a(17) =265092a(18) =524364a(19) =1053616a(20) =2098200a(21) =4202760a(22) =8388700a(23) =16797216a(24) =33554902a(25) =67141944a(26) =134221232a(27) =268503312a(28) =536871028a(29) =1073881488