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

Terms

a(0) =1a(1) =3a(2) =4a(3) =13a(4) =6a(5) =66a(6) =8a(7) =201a(8) =253a(9) =648a(10) =12a(11) =5488a(12) =14a(13) =8550a(14) =22824a(15) =49681a(16) =18a(17) =316743a(18) =20a(19) =865578a(20) =1611152a(21) =2098506a(22) =24a(23) =27246276a(24) =1953151a(25) =33556656a(26) =129199240a(27) =202152908a(28) =30a(29) =1758141606