a(n) = 12^n - 11^n.

Terms

a(0) =0a(1) =1a(2) =23a(3) =397a(4) =6095a(5) =87781a(6) =1214423a(7) =16344637a(8) =215622815a(9) =2801832661a(10) =35979939623a(11) =457696700077