a(n) = (-n)^(n-1).

Terms

a(0) =1a(1) =-2a(2) =9a(3) =-64a(4) =625a(5) =-7776a(6) =117649a(7) =-2097152a(8) =43046721a(9) =-1000000000a(10) =25937424601a(11) =-743008370688