a(n) = 1 - 10^n + 100^n.A168624a(n) = 1 - 10^n + 100^n.Terms a(0) =1a(1) =91a(2) =9901a(3) =999001a(4) =99990001a(5) =9999900001a(6) =999999000001External referencesoeis: A168624