43046737domain: NAppears in sequencesDirichlet convolution of 3^(n-1) with phi(n).at n=16A034754a(n) = 3^n + n.at n=16A1047433^(n^2)+2^n.at n=4A120798Number of empty faces in Freij's family of Hansen polytopes.at n=16A205646a(n) = Sum_{d|n} phi(n/d) * (-3)^(d-1).at n=16A383000