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

Terms

a(0) =1a(1) =5a(2) =13a(3) =41a(4) =81a(5) =245a(6) =449a(7) =1185a(8) =2413a(9) =5585a(10) =11265a(11) =26693a(12) =53249a(13) =118081a(14) =248733a(15) =535041a(16) =1114113a(17) =2390885a(18) =4980737a(19) =10557201a(20) =22050797a(21) =46265345a(22) =96468993a(23) =201795717a(24) =419480401a(25) =873123841a(26) =1812204685a(27) =3760019521a(28) =7784628225a(29) =16111126325