a(n) = Sum_{k=1..n} gcd(k,n)^(n-2).

Terms

a(0) =1a(1) =2a(2) =5a(3) =22a(4) =129a(5) =1411a(6) =16813a(7) =266372a(8) =4787349a(9) =100391653a(10) =2357947701a(11) =61980047702