a(n) = Sum_{ d divides n } (n/d)^(3d).

Terms

a(0) =1a(1) =9a(2) =28a(3) =129a(4) =126a(5) =1458a(6) =344a(7) =8705a(8) =20413a(9) =49394a(10) =1332a(11) =1104114a(12) =2198a(13) =2217546a(14) =16305408a(15) =33820673a(16) =4914a(17) =532253187a(18) =6860a(19) =2392632274a(20) =10500716072a(21) =8591716802a(22) =12168a(23) =422182489826a(24) =30517593751a(25) =549760658274