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

Terms

a(0) =1a(1) =3a(2) =7a(3) =13a(4) =21a(5) =39a(6) =43a(7) =81a(8) =109a(9) =173a(10) =111a(11) =475a(12) =157a(13) =507a(14) =1107a(15) =1153a(16) =273a(17) =2997a(18) =343a(19) =6133a(20) =6685a(21) =3479a(22) =507a(23) =30819a(24) =13001a(25) =10533a(26) =44227a(27) =65071a(28) =813a(29) =234959