a(n) = Sum_{d|n} (-1)^(n/d+1) * d^(n-d).

Terms

a(0) =1a(1) =0a(2) =2a(3) =-4a(4) =2a(5) =-11a(6) =2a(7) =-320a(8) =731a(9) =-2869a(10) =2a(11) =-1827a(12) =2a(13) =-819447a(14) =10297068a(15) =-33570816a(16) =2a(17) =1775078476a(18) =2a(19) =-36222872973a(20) =678610493340a(21) =-285310622035a(22) =2a(28) =2a(30) =2