a(n) = Sum_{d|n} mu(d)^2*d^n.

Terms

a(0) =1a(1) =5a(2) =28a(3) =17a(4) =3126a(5) =47450a(6) =823544a(7) =257a(8) =19684a(9) =10009766650a(10) =285311670612a(11) =2177317874a(15) =65537