a(n) = Sum_{d|n} phi(d)*5^(n/d).

Terms

a(0) =0a(1) =5a(2) =30a(3) =135a(4) =660a(5) =3145a(6) =15810a(7) =78155a(8) =391320a(9) =1953405a(10) =9768870a(11) =48828175a(12) =244157820a(13) =1220703185a(14) =6103593930a(15) =30517584915a(16) =152588282640a(17) =762939453205