a(n) = 9*a(n-1) + 10*a(n-2).

Terms

a(0) =0a(1) =1a(2) =9a(3) =91a(4) =909a(5) =9091a(6) =90909a(7) =909091a(8) =9090909a(9) =90909091a(10) =909090909a(11) =9090909091a(12) =90909090909a(13) =909090909091