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

Terms

a(0) =1a(1) =4a(2) =9a(3) =24a(4) =25a(5) =120a(6) =49a(7) =144a(8) =135a(9) =540a(10) =121a(11) =1728a(12) =169a(13) =1456a(14) =2145a(15) =800a(16) =289a(17) =5220a(18) =361a(19) =8840a(20) =5985a(21) =5544a(22) =529a(23) =21216a(24) =1125a(25) =9100a(26) =1863a(27) =25200a(28) =841a(29) =252000