a(n) = Sum_{d|n} phi(d^3).

Terms

a(0) =1a(1) =5a(2) =19a(3) =37a(4) =101a(5) =95a(6) =295a(7) =293a(8) =505a(9) =505a(10) =1211a(11) =703a(12) =2029a(13) =1475a(14) =1919a(15) =2341a(16) =4625a(17) =2525a(18) =6499a(19) =3737a(20) =5605a(21) =6055a(22) =11639a(23) =5567a(24) =12601a(25) =10145a(26) =13627a(27) =10915a(28) =23549a(29) =9595