a(n) = Sum_{d|8} phi(d)*n^(8/d).

Terms

a(0) =0a(1) =8a(2) =288a(3) =6672a(4) =65840a(5) =391320a(6) =1681008a(7) =5767328a(8) =16781472a(9) =43053480a(10) =100010240a(11) =214373808a(12) =430002768a(13) =815759672a(14) =1475827920a(15) =2562941760a(16) =4295033408a(17) =6975841608a(18) =11020066272a(19) =16983694160a(20) =25600160880a(21) =37823054808a(22) =54876108848