a(n) = 11^n - 10^n.

Terms

a(0) =0a(1) =1a(2) =21a(3) =331a(4) =4641a(5) =61051a(6) =771561a(7) =9487171a(8) =114358881a(9) =1357947691a(10) =15937424601a(11) =185311670611