a(n) = Sum_{d|n} mu(n/d) * d * (n/d)^(d-1), where mu() is the Moebius function (A008683).

Terms

a(0) =1a(1) =1a(2) =2a(3) =0a(4) =4a(5) =-11a(6) =6a(7) =-24a(8) =-18a(9) =-79a(10) =10a(11) =-276a(12) =12a(13) =-447a(14) =-464a(15) =-1008a(16) =16a(17) =-3636a(18) =18a(19) =-5580a(20) =-5228a(21) =-11263a(22) =22a(23) =-41184a(24) =-3100a(25) =-53247a(26) =-59022a(27) =-116004a(28) =28a(29) =-454501