a(n) = 11^n - 9^n.

Terms

a(0) =0a(1) =2a(2) =40a(3) =602a(4) =8080a(5) =102002a(6) =1240120a(7) =14704202a(8) =171312160a(9) =1970527202a(10) =22450640200a(11) =253930611002