a(n) = Sum_{k=1..n} gcd(k, n)^7.

Terms

a(0) =1a(1) =129a(2) =2189a(3) =16514a(4) =78129a(5) =282381a(6) =823549a(7) =2113796a(8) =4787349a(9) =10078641a(10) =19487181a(11) =36149146a(12) =62748529a(13) =106237821a(14) =171024381a(15) =270565896a(16) =410338689a(17) =617568021a(18) =893871757a(19) =1290222306a(20) =1802748761a(21) =2513846349a(22) =3404825469a(23) =4627099444a(24) =6103828145a(25) =8094560241