a(n) = (9*10^n + (-10)^n)/10.

Terms

a(0) =1a(1) =8a(2) =100a(3) =800a(4) =10000a(5) =80000a(6) =1000000a(7) =8000000a(8) =100000000a(9) =800000000a(10) =10000000000a(11) =80000000000a(12) =1000000000000