a(n) = Sum_{p|n, p prime} p^lcm(p,n/p).

Terms

a(0) =0a(1) =4a(2) =27a(3) =4a(4) =3125a(5) =793a(6) =823543a(7) =16a(8) =27a(9) =9766649a(10) =285311670611a(11) =531505a(13) =678223089233a(14) =30531927032a(15) =256a(17) =262873