a(n) = 11^n - 8^n.

Terms

a(0) =0a(1) =3a(2) =57a(3) =819a(4) =10545a(5) =128283a(6) =1509417a(7) =17390019a(8) =197581665a(9) =2223729963a(10) =24863682777a(11) =276721736019